Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....

I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
Thanks
J

On Thursday, December 29, 2022 at 1:04:27 PM UTC-5, jjhu...@gmail.com wrote:
> Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
> I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
> I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
>
> I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?

I'm willing to bet you are going to need to roll your own in an FPGA, with analog circuitry to handle the signals from the heads. I don't know exactly what the FDC does, do you? I guess if you have an interface spec, and especially source code for the driver, you can reverse engineer from that.

You might try finding computer hobbyist groups on Facebook, Linkedin and the like. I'm willing to bet someone has done this before to keep some gear running.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

On Thursday, December 29, 2022 at 10:15:57 AM UTC-8, Ricky wrote:
> On Thursday, December 29, 2022 at 1:04:27 PM UTC-5, jjhu...@gmail.com wrote:
> > Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
> > I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
> > I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
> >
> > I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
> I'm willing to bet you are going to need to roll your own in an FPGA, with analog circuitry to handle the signals from the heads. I don't know exactly what the FDC does, do you? I guess if you have an interface spec, and especially source code for the driver, you can reverse engineer from that.

I don't know too much either, but i know it's slow. I bet you can do it with high end micro, rather than FPGA.

On 12/29/2022 20:15, Ricky wrote:
> On Thursday, December 29, 2022 at 1:04:27 PM UTC-5, jjhu...@gmail.com wrote:
>> Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
>> I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
>> I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
>>
>> I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
>
> I'm willing to bet you are going to need to roll your own in an FPGA, with analog circuitry to handle the signals from the heads. I don't know exactly what the FDC does, do you? I guess if you have an interface spec, and especially source code for the driver, you can reverse engineer from that.
>
> You might try finding computer hobbyist groups on Facebook, Linkedin and the like. I'm willing to bet someone has done this before to keep some gear running.
>

There are no analog signals coming from the floppy drives as we know
them. Back in the 80-s I did two controllers, 765 based. It is all
TTL to/from the floppy.

On Thursday, December 29, 2022 at 10:46:58 AM UTC-8, Dimiter Popoff wrote:
> On 12/29/2022 20:15, Ricky wrote:
> > On Thursday, December 29, 2022 at 1:04:27 PM UTC-5, jjhu...@gmail.com wrote:
> >> Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
> >> I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
> >> I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
> >>
> >> I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
> >
> > I'm willing to bet you are going to need to roll your own in an FPGA, with analog circuitry to handle the signals from the heads. I don't know exactly what the FDC does, do you? I guess if you have an interface spec, and especially source code for the driver, you can reverse engineer from that.
> >
> > You might try finding computer hobbyist groups on Facebook, Linkedin and the like. I'm willing to bet someone has done this before to keep some gear running.

Talking to the FDC is very different from talking to FDD.

> There are no analog signals coming from the floppy drives as we know
> them. Back in the 80-s I did two controllers, 765 based. It is all
> TTL to/from the floppy.

Just need some circuit to read/write MFM signal, and controlling the stepper motor.

On 12/29/2022 11:04 AM, Three Jeeps wrote:
> Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
> I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
> I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
>
> I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
> Thanks

The "Zilog Development Systems" in the 70's basically just grabbed bits off
the head using a vintage Z80. It spent most of real-time doing that. But,
nowadays, that would just be a "side job".

You might try hunting down schemes from them to see what their hardware
entailed.

On Thursday, December 29, 2022 at 11:05:30 AM UTC-8, Don Y wrote:
> On 12/29/2022 11:04 AM, Three Jeeps wrote:
> > Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
> > I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
> > I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
> >
> > I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
> > Thanks
> The "Zilog Development Systems" in the 70's basically just grabbed bits off
> the head using a vintage Z80. It spent most of real-time doing that. But,
> nowadays, that would just be a "side job".
>
> You might try hunting down schemes from them to see what their hardware
> entailed.

Crystal clock, PLL and magnetic reader/writer.

On 12/29/2022 20:50, Ed Lee wrote:
> On Thursday, December 29, 2022 at 10:46:58 AM UTC-8, Dimiter Popoff wrote:
>> On 12/29/2022 20:15, Ricky wrote:
>>> On Thursday, December 29, 2022 at 1:04:27 PM UTC-5, jjhu...@gmail.com wrote:
>>>> Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
>>>> I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
>>>> I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
>>>>
>>>> I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
>>>
>>> I'm willing to bet you are going to need to roll your own in an FPGA, with analog circuitry to handle the signals from the heads. I don't know exactly what the FDC does, do you? I guess if you have an interface spec, and especially source code for the driver, you can reverse engineer from that.
>>>
>>> You might try finding computer hobbyist groups on Facebook, Linkedin and the like. I'm willing to bet someone has done this before to keep some gear running.
>
> Talking to the FDC is very different from talking to FDD.
>
>> There are no analog signals coming from the floppy drives as we know
>> them. Back in the 80-s I did two controllers, 765 based. It is all
>> TTL to/from the floppy.
>
> Just need some circuit to read/write MFM signal, and controlling the stepper motor.

With the 765 I did that with a few TTL parts back then, one had to do
the clock recovery (for either FM or MFM) The interface to the FDD was
standard, still is if anybody makes them...
Back in the early 90-s I had a SCSI floppy, my newer machines had no
FDC. It was really well made, I could talk it into reading the floppies
from my older machines which I used with 256 bytes/sector; all the gaps
etc. thing was programmable over SCSI. Cost something like $300, I still
sort of mourn it... (killed it with a shitty scsi cable I had
made. I have no floppies to read, moved all I wanted to images as
files on my disks (some while I still had that scsi FDD) but I
still mourn it when I think of it :-).

Three Jeeps <jjhudak4@gmail.com> wrote:
> Back in the day, I wrote a floppy driver based on the 82077AA for a board
> I designed. The 82077AA is long gone and I've been away from hardware
> engineering at this level for a while. I am doing a spare time project
> where I'd like to revive the FD driver in conjunction with a small SBC. I
> am wondering what the current chip is that is close to being functionally
> equivalent to the 82077AA that can actually be bought today?
> I did some searching and found the Microchip FDC37C78-HT but it seems to
> be unavailable. There are other FDCs around at the time that were quite
> popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too
> are long gone/unabtanium. I like the intel 82077AA because it could
> interface to a large number of FDCs.
> I also am considering to throw a FPGA at it, but that would probably be
> more work than I wanted to devote to it....
>
> I'll keep searching but in the interim I thought maybe someone here may
> have some thoughts/pointers to FDCs that are currently available?
> Thanks

There are plenty of 82077AA devices on eBay if you only need few of those. I
would even bet they are not fakes as it is not one of high-demand expensive
devices.

---
******************************************************************
* KSI@home KOI8 Net < > The impossible we do immediately. *
* Las Vegas NV, USA < > Miracles require 24-hour notice. *
******************************************************************

On Thursday, December 29, 2022 at 1:46:58 PM UTC-5, Dimiter Popoff wrote:
> On 12/29/2022 20:15, Ricky wrote:
> > On Thursday, December 29, 2022 at 1:04:27 PM UTC-5, jjhu...@gmail.com wrote:
> >> Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
> >> I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
> >> I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
> >>
> >> I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
> >
> > I'm willing to bet you are going to need to roll your own in an FPGA, with analog circuitry to handle the signals from the heads. I don't know exactly what the FDC does, do you? I guess if you have an interface spec, and especially source code for the driver, you can reverse engineer from that.
> >
> > You might try finding computer hobbyist groups on Facebook, Linkedin and the like. I'm willing to bet someone has done this before to keep some gear running.
> >
> There are no analog signals coming from the floppy drives as we know
> them. Back in the 80-s I did two controllers, 765 based. It is all
> TTL to/from the floppy.

So the floppy drive itself has electronics to recover the data from the head signal?

If that's so, you probably can interface to a floppy with an MCU. The harder part might be the interface to the other side, but if you can specify that yourself, you should be good to go with something simple like SPI with a custom protocol.

--

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209

On Thursday, December 29, 2022 at 1:50:46 PM UTC-5, Ed Lee wrote:
> On Thursday, December 29, 2022 at 10:46:58 AM UTC-8, Dimiter Popoff wrote:
> > On 12/29/2022 20:15, Ricky wrote:
> > > On Thursday, December 29, 2022 at 1:04:27 PM UTC-5, jjhu...@gmail.com wrote:
> > >> Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
> > >> I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
> > >> I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
> > >>
> > >> I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
> > >
> > > I'm willing to bet you are going to need to roll your own in an FPGA, with analog circuitry to handle the signals from the heads. I don't know exactly what the FDC does, do you? I guess if you have an interface spec, and especially source code for the driver, you can reverse engineer from that..
> > >
> > > You might try finding computer hobbyist groups on Facebook, Linkedin and the like. I'm willing to bet someone has done this before to keep some gear running.
> Talking to the FDC is very different from talking to FDD.
> > There are no analog signals coming from the floppy drives as we know
> > them. Back in the 80-s I did two controllers, 765 based. It is all
> > TTL to/from the floppy.
> Just need some circuit to read/write MFM signal, and controlling the stepper motor.

MFM at reasonable data rates is easily done in an MCU.

--

Rick C.

-- Get 1,000 miles of free Supercharging
-- Tesla referral code - https://ts.la/richard11209

On 12/30/2022 0:28, Ricky wrote:
> On Thursday, December 29, 2022 at 1:46:58 PM UTC-5, Dimiter Popoff wrote:
>> On 12/29/2022 20:15, Ricky wrote:
>>> On Thursday, December 29, 2022 at 1:04:27 PM UTC-5, jjhu...@gmail.com wrote:
>>>> Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
>>>> I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
>>>> I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
>>>>
>>>> I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
>>>
>>> I'm willing to bet you are going to need to roll your own in an FPGA, with analog circuitry to handle the signals from the heads. I don't know exactly what the FDC does, do you? I guess if you have an interface spec, and especially source code for the driver, you can reverse engineer from that.
>>>
>>> You might try finding computer hobbyist groups on Facebook, Linkedin and the like. I'm willing to bet someone has done this before to keep some gear running.
>>>
>> There are no analog signals coming from the floppy drives as we know
>> them. Back in the 80-s I did two controllers, 765 based. It is all
>> TTL to/from the floppy.
>
> So the floppy drive itself has electronics to recover the data from the head signal?

Not exactly the data, just to make a TTL bitstream out of what the R/W
head reads - and to record in the opposite direction.
How that stream is divided into sectors, gaps between them etc. is the
job of a disk controller, in my case it was a upd765.

> If that's so, you probably can interface to a floppy with an MCU. The harder part might be the interface to the other side, but if you can specify that yourself, you should be good to go with something simple like SPI with a custom protocol.

Possibly but it won't be an easy ride. IIRC the bit stream is 1 MHz
clocked, was it 2 at high density (don't remember). Then it is coming
from a mechanically rotating media plus noise so clock recovery is
not the easiest thing to do - but doable, I think what I did was
to reset a counter or something to stay in sync, was simple anyway
and worked rock stable. Don says it has been all done with a Z80,
which must have been quite an achievement if it could do standard
MFM floppies.
My achievement was to make a 1 MHz 6809 read the data from the
765 at highest speed it could come without using a DMA (prior
to that I had done it with one, the 6844) and servicing the interrupts
in the gaps between the sectors, was anything but trivial to do.
(I think the highest speed data would come from a 5" HD floppy,
they rotated somewhat faster at the highest density).
>

torsdag den 29. december 2022 kl. 23.52.51 UTC+1 skrev Dimiter Popoff:
> On 12/30/2022 0:28, Ricky wrote:
> > On Thursday, December 29, 2022 at 1:46:58 PM UTC-5, Dimiter Popoff wrote:
> >> On 12/29/2022 20:15, Ricky wrote:
> >>> On Thursday, December 29, 2022 at 1:04:27 PM UTC-5, jjhu...@gmail.com wrote:
> >>>> Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
> >>>> I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
> >>>> I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
> >>>>
> >>>> I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
> >>>
> >>> I'm willing to bet you are going to need to roll your own in an FPGA, with analog circuitry to handle the signals from the heads. I don't know exactly what the FDC does, do you? I guess if you have an interface spec, and especially source code for the driver, you can reverse engineer from that..
> >>>
> >>> You might try finding computer hobbyist groups on Facebook, Linkedin and the like. I'm willing to bet someone has done this before to keep some gear running.
> >>>
> >> There are no analog signals coming from the floppy drives as we know
> >> them. Back in the 80-s I did two controllers, 765 based. It is all
> >> TTL to/from the floppy.
> >
> > So the floppy drive itself has electronics to recover the data from the head signal?
> Not exactly the data, just to make a TTL bitstream out of what the R/W
> head reads - and to record in the opposite direction.
> How that stream is divided into sectors, gaps between them etc. is the
> job of a disk controller, in my case it was a upd765.
> > If that's so, you probably can interface to a floppy with an MCU. The harder part might be the interface to the other side, but if you can specify that yourself, you should be good to go with something simple like SPI with a custom protocol.
> Possibly but it won't be an easy ride. IIRC the bit stream is 1 MHz
> clocked, was it 2 at high density (don't remember). Then it is coming
> from a mechanically rotating media plus noise so clock recovery is
> not the easiest thing to do - but doable, I think what I did was
> to reset a counter or something to stay in sync, was simple anyway
> and worked rock stable. Don says it has been all done with a Z80,
> which must have been quite an achievement if it could do standard
> MFM floppies.
> My achievement was to make a 1 MHz 6809 read the data from the
> 765 at highest speed it could come without using a DMA (prior
> to that I had done it with one, the 6844) and servicing the interrupts
> in the gaps between the sectors, was anything but trivial to do.
> (I think the highest speed data would come from a 5" HD floppy,
> they rotated somewhat faster at the highest density).
> >

https://www.5volts.ch/posts/mfmreader/

On Thursday, December 29, 2022 at 1:15:57 PM UTC-5, Ricky wrote:
> On Thursday, December 29, 2022 at 1:04:27 PM UTC-5, jjhu...@gmail.com wrote:
> > Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
> > I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
> > I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
> >
> > I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
> I'm willing to bet you are going to need to roll your own in an FPGA, with analog circuitry to handle the signals from the heads. I don't know exactly what the FDC does, do you? I guess if you have an interface spec, and especially source code for the driver, you can reverse engineer from that.
>
> You might try finding computer hobbyist groups on Facebook, Linkedin and the like. I'm willing to bet someone has done this before to keep some gear running.
>
> --
>
> Rick C.
>
> - Get 1,000 miles of free Supercharging
> - Tesla referral code - https://ts.la/richard11209

Perhaps I was not clear. The FDC IC controls the data transfer from the disk to the MCU. The disk drive proper contains the analog electronics to position the heads (most often a stepper motor), and pull out the data. The floppy disk controller does not contain any analog processing components and head positioning software/hardware, all that is done on the drive itself.
Yes, a high end micro could probably do the job, but the FDC is a 'cleaner' approach...and if I had to go a different route, I'd use an FPGA instead of the micro. I do have the data sheets for many of the FDC chips of that era, including the 82077AA. While I've done it before for DEC RK07 drives, I don't want to reinvent the wheel on a FPGA if I don't have to.

On 12/30/2022 1:00, Lasse Langwadt Christensen wrote:
> torsdag den 29. december 2022 kl. 23.52.51 UTC+1 skrev Dimiter Popoff:
>> On 12/30/2022 0:28, Ricky wrote:
>>> On Thursday, December 29, 2022 at 1:46:58 PM UTC-5, Dimiter Popoff wrote:
>>>> On 12/29/2022 20:15, Ricky wrote:
>>>>> On Thursday, December 29, 2022 at 1:04:27 PM UTC-5, jjhu...@gmail.com wrote:
>>>>>> Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
>>>>>> I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
>>>>>> I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
>>>>>>
>>>>>> I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
>>>>>
>>>>> I'm willing to bet you are going to need to roll your own in an FPGA, with analog circuitry to handle the signals from the heads. I don't know exactly what the FDC does, do you? I guess if you have an interface spec, and especially source code for the driver, you can reverse engineer from that.
>>>>>
>>>>> You might try finding computer hobbyist groups on Facebook, Linkedin and the like. I'm willing to bet someone has done this before to keep some gear running.
>>>>>
>>>> There are no analog signals coming from the floppy drives as we know
>>>> them. Back in the 80-s I did two controllers, 765 based. It is all
>>>> TTL to/from the floppy.
>>>
>>> So the floppy drive itself has electronics to recover the data from the head signal?
>> Not exactly the data, just to make a TTL bitstream out of what the R/W
>> head reads - and to record in the opposite direction.
>> How that stream is divided into sectors, gaps between them etc. is the
>> job of a disk controller, in my case it was a upd765.
>>> If that's so, you probably can interface to a floppy with an MCU. The harder part might be the interface to the other side, but if you can specify that yourself, you should be good to go with something simple like SPI with a custom protocol.
>> Possibly but it won't be an easy ride. IIRC the bit stream is 1 MHz
>> clocked, was it 2 at high density (don't remember). Then it is coming
>> from a mechanically rotating media plus noise so clock recovery is
>> not the easiest thing to do - but doable, I think what I did was
>> to reset a counter or something to stay in sync, was simple anyway
>> and worked rock stable. Don says it has been all done with a Z80,
>> which must have been quite an achievement if it could do standard
>> MFM floppies.
>> My achievement was to make a 1 MHz 6809 read the data from the
>> 765 at highest speed it could come without using a DMA (prior
>> to that I had done it with one, the 6844) and servicing the interrupts
>> in the gaps between the sectors, was anything but trivial to do.
>> (I think the highest speed data would come from a 5" HD floppy,
>> they rotated somewhat faster at the highest density).
>>>
>
> > https://www.5volts.ch/posts/mfmreader/

Hah! This guy has put in the effort and made it, did not know someone
would be into that sort of thing. Like I said not an easy ride, but he
has done it all, bravo.

On 12/29/2022 3:50 PM, Dimiter_Popoff wrote:
> Possibly but it won't be an easy ride. IIRC the bit stream is 1 MHz
> clocked, was it 2 at high density (don't remember). Then it is coming
> from a mechanically rotating media plus noise so clock recovery is
> not the easiest thing to do - but doable, I think what I did was
> to reset a counter or something to stay in sync, was simple anyway
> and worked rock stable. Don says it has been all done with a Z80,
> which must have been quite an achievement if it could do standard
> MFM floppies.

The ZDS used 8" *hard* sectored floppies. And, they were dog slow.
The processor basically just sat watching the index and sector holes
on the disk (to find the correct sector) and then just sopping up
the bits coming off the disk. No such thing as overlapped I/O :>

"Back then", it was common to have access to the schematics and source
code for the development tools; the manufacturers were in the business
of selling *chips* and only made development systems as a "cost of
doing (that) business". So, I looked at both (HW/SW) to see where
we were "waiting" (engineers' time being far more expensive than
the cost of tools).

IIRC, RIO? (the OS that ran on the boxes) was designed to support
multitasking but the horsepower just wasn't there to *do* much.

I designed a CP/M-based development system as a replacement for
them and it was like suddenly having air conditioning in the desert!

> My achievement was to make a 1 MHz 6809 read the data from the
> 765 at highest speed it could come without using a DMA (prior
> to that I had done it with one, the 6844) and servicing the interrupts
> in the gaps between the sectors, was anything but trivial to do.
> (I think the highest speed data would come from a 5" HD floppy,
> they rotated somewhat faster at the highest density).

On 12/29/2022 12:08 PM, Ed Lee wrote:
> On Thursday, December 29, 2022 at 11:05:30 AM UTC-8, Don Y wrote:
>> On 12/29/2022 11:04 AM, Three Jeeps wrote:
>>> Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
>>> I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
>>> I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
>>>
>>> I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
>>> Thanks
>> The "Zilog Development Systems" in the 70's basically just grabbed bits off
>> the head using a vintage Z80. It spent most of real-time doing that. But,
>> nowadays, that would just be a "side job".
>>
>> You might try hunting down schemes from them to see what their hardware
>> entailed.
>
> Crystal clock, PLL and magnetic reader/writer.

No. You can do all that in software -- if the processor focuses on
the task (you're dealing with digital signals to/from the diskette).

It's comparable to reading barcodes with just a white/black input
to a processor -- you notice *when* it changes state and, later,
sort out what that *series* of changes actually means.

[The Z80's CTC's were perfect for this sort of task as you
could use a single input channel to detect the transition
(programmed as hi-lo or lo-hi) AND interrupt when that
occurred *and* how long ago this was wrt some notion of
"system time". More modern counter/timers have been bred
for simplicity. :< ]

On 12/29/2022 12:12 PM, Dimiter_Popoff wrote:
> Back in the early 90-s I had a SCSI floppy, my newer machines had no

(sigh) I would welcome that for my Sun boxen. There are times
when the floppy disk is the easiest way to get around a boot problem!
(their mechanisms tend to get gummed up due to age and disuse)

> FDC. It was really well made, I could talk it into reading the floppies
> from my older machines which I used with 256 bytes/sector; all the gaps
> etc. thing was programmable over SCSI. Cost something like $300, I still
> sort of mourn it... (killed it with a shitty scsi cable I had
> made. I have no floppies to read, moved all I wanted to images as
> files on my disks (some while I still had that scsi FDD) but I
> still mourn it when I think of it :-).

I keep 8, 5 and 3" drives and a bit of media. Mostly out of
habit (I PXE boot most machines if hard disk issues and only
have one box that uses *8"* floppies; my PROM programmer
uses 720K 3" media -- to boot!)

fredag den 30. december 2022 kl. 01.24.05 UTC+1 skrev Don Y:
> On 12/29/2022 12:08 PM, Ed Lee wrote:
> > On Thursday, December 29, 2022 at 11:05:30 AM UTC-8, Don Y wrote:
> >> On 12/29/2022 11:04 AM, Three Jeeps wrote:
> >>> Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
> >>> I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
> >>> I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
> >>>
> >>> I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
> >>> Thanks
> >> The "Zilog Development Systems" in the 70's basically just grabbed bits off
> >> the head using a vintage Z80. It spent most of real-time doing that. But,
> >> nowadays, that would just be a "side job".
> >>
> >> You might try hunting down schemes from them to see what their hardware
> >> entailed.
> >
> > Crystal clock, PLL and magnetic reader/writer.
> No. You can do all that in software -- if the processor focuses on
> the task (you're dealing with digital signals to/from the diskette).
>
> It's comparable to reading barcodes with just a white/black input
> to a processor -- you notice *when* it changes state and, later,
> sort out what that *series* of changes actually means.
>
> [The Z80's CTC's were perfect for this sort of task as you
> could use a single input channel to detect the transition
> (programmed as hi-lo or lo-hi) AND interrupt when that
> occurred *and* how long ago this was wrt some notion of
> "system time". More modern counter/timers have been bred
> for simplicity. :< ]

you must not have seen many modern timers

On Thursday, December 29, 2022 at 6:10:05 PM UTC-5, Three Jeeps wrote:
> On Thursday, December 29, 2022 at 1:15:57 PM UTC-5, Ricky wrote:
> > On Thursday, December 29, 2022 at 1:04:27 PM UTC-5, jjhu...@gmail.com wrote:
> > > Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
> > > I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
> > > I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
> > >
> > > I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
> > I'm willing to bet you are going to need to roll your own in an FPGA, with analog circuitry to handle the signals from the heads. I don't know exactly what the FDC does, do you? I guess if you have an interface spec, and especially source code for the driver, you can reverse engineer from that.
> >
> > You might try finding computer hobbyist groups on Facebook, Linkedin and the like. I'm willing to bet someone has done this before to keep some gear running.
> >
> > --
> >
> > Rick C.
> >
> > - Get 1,000 miles of free Supercharging
> > - Tesla referral code - https://ts.la/richard11209
> Perhaps I was not clear. The FDC IC controls the data transfer from the disk to the MCU. The disk drive proper contains the analog electronics to position the heads (most often a stepper motor), and pull out the data. The floppy disk controller does not contain any analog processing components and head positioning software/hardware, all that is done on the drive itself.
> Yes, a high end micro could probably do the job, but the FDC is a 'cleaner' approach...and if I had to go a different route, I'd use an FPGA instead of the micro. I do have the data sheets for many of the FDC chips of that era, including the 82077AA. While I've done it before for DEC RK07 drives, I don't want to reinvent the wheel on a FPGA if I don't have to.

One additional point. I firmly believe that controlling devices at the basic level should be the job of hardware. It is a logical separation of concerns as well as reducing cpu utilization to other jobs the processor can do instead of bit banging a disk drive (or what ever). Maintaining sequencing and timing of signals is efficiently done by hardware, leaving the CPU to handle other tasks. Yea, could throw a processor at it as the controller but that would muddy up the architecture (hardware and sw) of the system I am working with.

On Thursday, December 29, 2022 at 6:02:14 PM UTC-8, jjhu...@gmail.com wrote:
> On Thursday, December 29, 2022 at 6:10:05 PM UTC-5, Three Jeeps wrote:
> > On Thursday, December 29, 2022 at 1:15:57 PM UTC-5, Ricky wrote:
> > > On Thursday, December 29, 2022 at 1:04:27 PM UTC-5, jjhu...@gmail.com wrote:
> > > > Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
> > > > I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
> > > > I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
> > > >
> > > > I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
> > > I'm willing to bet you are going to need to roll your own in an FPGA, with analog circuitry to handle the signals from the heads. I don't know exactly what the FDC does, do you? I guess if you have an interface spec, and especially source code for the driver, you can reverse engineer from that..
> > >
> > > You might try finding computer hobbyist groups on Facebook, Linkedin and the like. I'm willing to bet someone has done this before to keep some gear running.
> > >
> > > --
> > >
> > > Rick C.
> > >
> > > - Get 1,000 miles of free Supercharging
> > > - Tesla referral code - https://ts.la/richard11209
> > Perhaps I was not clear. The FDC IC controls the data transfer from the disk to the MCU. The disk drive proper contains the analog electronics to position the heads (most often a stepper motor), and pull out the data. The floppy disk controller does not contain any analog processing components and head positioning software/hardware, all that is done on the drive itself..
> > Yes, a high end micro could probably do the job, but the FDC is a 'cleaner' approach...and if I had to go a different route, I'd use an FPGA instead of the micro. I do have the data sheets for many of the FDC chips of that era, including the 82077AA. While I've done it before for DEC RK07 drives, I don't want to reinvent the wheel on a FPGA if I don't have to.
> One additional point. I firmly believe that controlling devices at the basic level should be the job of hardware. It is a logical separation of concerns as well as reducing cpu utilization to other jobs the processor can do instead of bit banging a disk drive (or what ever). Maintaining sequencing and timing of signals is efficiently done by hardware, leaving the CPU to handle other tasks. Yea, could throw a processor at it as the controller but that would muddy up the architecture (hardware and sw) of the system I am working with.

Those were the days when memory was limited. But for today's system, if you even want to use floppy, would be to load everything into memory while booting. While booting, your CPU would not be doing any other task.

On 12/29/2022 5:54 PM, Lasse Langwadt Christensen wrote:
> fredag den 30. december 2022 kl. 01.24.05 UTC+1 skrev Don Y:
>> On 12/29/2022 12:08 PM, Ed Lee wrote:
>>> On Thursday, December 29, 2022 at 11:05:30 AM UTC-8, Don Y wrote:
>>>> On 12/29/2022 11:04 AM, Three Jeeps wrote:
>>>>> Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
>>>>> I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
>>>>> I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
>>>>>
>>>>> I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
>>>>> Thanks
>>>> The "Zilog Development Systems" in the 70's basically just grabbed bits off
>>>> the head using a vintage Z80. It spent most of real-time doing that. But,
>>>> nowadays, that would just be a "side job".
>>>>
>>>> You might try hunting down schemes from them to see what their hardware
>>>> entailed.
>>>
>>> Crystal clock, PLL and magnetic reader/writer.
>> No. You can do all that in software -- if the processor focuses on
>> the task (you're dealing with digital signals to/from the diskette).
>>
>> It's comparable to reading barcodes with just a white/black input
>> to a processor -- you notice *when* it changes state and, later,
>> sort out what that *series* of changes actually means.
>>
>> [The Z80's CTC's were perfect for this sort of task as you
>> could use a single input channel to detect the transition
>> (programmed as hi-lo or lo-hi) AND interrupt when that
>> occurred *and* how long ago this was wrt some notion of
>> "system time". More modern counter/timers have been bred
>> for simplicity. :< ]
>
> you must not have seen many modern timers

Modern timers have a shitload of logic to implement simple concepts.

The CTC had a counter and a "time constant" register. No capture
register, preload register, etc. The input could be "counted"
or used to enable the timer (edge/level). The timer could be
preloaded with ValueX and the Time Constant Register preloaded
with ValueY. So, when activated (triggered) it would count down
from X and *then* count down from Y (so, you could preload it with
'1' and a TCR of "256", set the input to be an enable on a specific
edge and get an IRQ after the *first* edge detected -- while the
counter would reload from 256 and continue counting). The TCR
could be used as a divider to develop various output frequencies.

Look at the modern equivalent of all these features and the amount
of logic dedicated to provide that same (not more!) functionality.
No need for match registers, capture registers, etc.

Given 40 years of technological advances, user experience and die
shrinks, it's a wonder they don't put 9513's on each MCU! If you're
going to use silicon to implement a feature, use it to implement
things that can't otherwise be implemented.

On a sunny day (Thu, 29 Dec 2022 10:04:23 -0800 (PST)) it happened Three Jeeps
<jjhudak4@gmail.com> wrote in
<7bd48288-ee79-47ed-8daa-37ff02733534n@googlegroups.com>:

>Back in the day, I wrote a floppy driver based on the 82077AA for a board I
>designed. The 82077AA is long gone and I've been away from hardware engineering
>at this level for a while. I am doing a spare time project where I'd
>like to revive the FD driver in conjunction with a small SBC. I am wondering
>what the current chip is that is close to being functionally equivalent
>to the 82077AA that can actually be bought today?
>I did some searching and found the Microchip FDC37C78-HT but it seems to be
>unavailable. There are other FDCs around at the time that were quite popular
>(e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long
>gone/unabtanium. I like the intel 82077AA because it could interface to
>a large number of FDCs.
>I also am considering to throw a FPGA at it, but that would probably be more
>work than I wanted to devote to it....
>
>I'll keep searching but in the interim I thought maybe someone here may have
>some thoughts/pointers to FDCs that are currently available?
>Thanks
>J

As somebody else suggested: ebay for the chip.
That said I wrote a driver for the 8072 and designed some hardware PLL
with a 4046
http://panteltje.com/panteltje/z80/system14/diagrams/index.html
scroll down to floppy disk controller.
http://panteltje.com/panteltje/z80/system14/diagrams/fdc-2.jpg

That was for 8 inch Kaypro II type floppies...

All that said, I still have an old PC with a floppy drive
and one day long ago bought an USB floppy drive.
That may be the fasted way,,,
But if you want to prove yourself ...

These days with 64 GB USB sticks and micro SD cards ...
recording HD movies on those...
Amazing.

On Thursday, December 29, 2022 at 5:52:51 PM UTC-5, Dimiter Popoff wrote:
> On 12/30/2022 0:28, Ricky wrote:
> > On Thursday, December 29, 2022 at 1:46:58 PM UTC-5, Dimiter Popoff wrote:
> >> On 12/29/2022 20:15, Ricky wrote:
> >>> On Thursday, December 29, 2022 at 1:04:27 PM UTC-5, jjhu...@gmail.com wrote:
> >>>> Back in the day, I wrote a floppy driver based on the 82077AA for a board I designed. The 82077AA is long gone and I've been away from hardware engineering at this level for a while. I am doing a spare time project where I'd like to revive the FD driver in conjunction with a small SBC. I am wondering what the current chip is that is close to being functionally equivalent to the 82077AA that can actually be bought today?
> >>>> I did some searching and found the Microchip FDC37C78-HT but it seems to be unavailable. There are other FDCs around at the time that were quite popular (e.g. NEC D765, intel 8272 and of course the WDC FDC) but they too are long gone/unabtanium. I like the intel 82077AA because it could interface to a large number of FDCs.
> >>>> I also am considering to throw a FPGA at it, but that would probably be more work than I wanted to devote to it....
> >>>>
> >>>> I'll keep searching but in the interim I thought maybe someone here may have some thoughts/pointers to FDCs that are currently available?
> >>>
> >>> I'm willing to bet you are going to need to roll your own in an FPGA, with analog circuitry to handle the signals from the heads. I don't know exactly what the FDC does, do you? I guess if you have an interface spec, and especially source code for the driver, you can reverse engineer from that..
> >>>
> >>> You might try finding computer hobbyist groups on Facebook, Linkedin and the like. I'm willing to bet someone has done this before to keep some gear running.
> >>>
> >> There are no analog signals coming from the floppy drives as we know
> >> them. Back in the 80-s I did two controllers, 765 based. It is all
> >> TTL to/from the floppy.
> >
> > So the floppy drive itself has electronics to recover the data from the head signal?
> Not exactly the data, just to make a TTL bitstream out of what the R/W
> head reads - and to record in the opposite direction.

Yes, that is what I mean. I didn't realize there was any electronics in the floppy drive itself. I've never paid close attention to the floppy interface. I was always more interested in the hard drive interfaces. They clearly have lots of on board electronics.

> How that stream is divided into sectors, gaps between them etc. is the
> job of a disk controller, in my case it was a upd765.
> > If that's so, you probably can interface to a floppy with an MCU. The harder part might be the interface to the other side, but if you can specify that yourself, you should be good to go with something simple like SPI with a custom protocol.
> Possibly but it won't be an easy ride. IIRC the bit stream is 1 MHz
> clocked, was it 2 at high density (don't remember). Then it is coming
> from a mechanically rotating media plus noise so clock recovery is
> not the easiest thing to do - but doable, I think what I did was
> to reset a counter or something to stay in sync, was simple anyway
> and worked rock stable. Don says it has been all done with a Z80,
> which must have been quite an achievement if it could do standard
> MFM floppies.

A Z80 is pretty slow compared to today's MCUs. That would be an interesting design to see.

I worked on a tape drive interface which was much slower than this, and done in logic, because we are talking the days of 8080s where a minimum design was more like a half dozen chips. I used to know details about all the serial formats, but they are lost in the haze. I know this was a simple one, like Manchester and only took a few chips of TTL. I believe timing was done by some fixed timing element, so a similar design would probably not be flexible enough for a floppy.

> My achievement was to make a 1 MHz 6809 read the data from the
> 765 at highest speed it could come without using a DMA (prior
> to that I had done it with one, the 6844) and servicing the interrupts
> in the gaps between the sectors, was anything but trivial to do.
> (I think the highest speed data would come from a 5" HD floppy,
> they rotated somewhat faster at the highest density).

I'm willing to bet an ARM CMx could be made to do the job. They clock pretty fast these days.

Talking about old technology, I remember meeting some guys who worked at NASA in Florida. They said that even today, it would not be possible to design the networked data distribution they had, using off the shelf computing and networking. They provided a few numbers and I would not argue with them. The Apollo system was all TTL and had pretty amazing stats. That was maybe 20 years ago, so maybe now with 10 or 100 Gbps networking... I don't know. I guess we'll never know. It's not like that will ever be built again.

--

Rick C.

-+ Get 1,000 miles of free Supercharging
-+ Tesla referral code - https://ts.la/richard11209

On a sunny day (Fri, 30 Dec 2022 03:57:52 GMT) it happened Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote in <tolr5r$j4s8$1@dont-email.me>:

>That was for 8 inch Kaypro II type floppies...

Oops. 5 1/4 inch and 8272 ..