https://arstechnica.com/gadgets/2022/03/a-brief-tour-of-the-pdp-11-the-most-influential-minicomputer-of-all-time/

On Monday, March 14, 2022 at 7:47:34 PM UTC-4, Arne Vajhøj wrote:
> https://arstechnica.com/gadgets/2022/03/a-brief-tour-of-the-pdp-11-the-most-influential-minicomputer-of-all-time/
Arne,

Not sure where the author of the arstechnica piece saw "$" for immediate mode, e.g., mov $10,r0. MACRO-11 as I new it, always used a "#", e.g., MOV #SS.XYZ,R0.

Spent lots of time writing and generating assembler for RSX-11 systems and relatives, e.g., P/OS. Did many interesting things.

- Bob Gezelter, http://www.rlgsc.com

On 3/14/2022 8:17 PM, Bob Gezelter wrote:
> On Monday, March 14, 2022 at 7:47:34 PM UTC-4, Arne Vajhøj wrote:
>> https://arstechnica.com/gadgets/2022/03/a-brief-tour-of-the-pdp-11-the-most-influential-minicomputer-of-all-time/
>
> Not sure where the author of the arstechnica piece saw "$" for immediate mode, e.g., mov $10,r0. MACRO-11 as I new it, always used a "#", e.g., MOV #SS.XYZ,R0.
>
> Spent lots of time writing and generating assembler for RSX-11 systems and relatives, e.g., P/OS. Did many interesting things.

I have never used a PDP-11 so I have no idea (I am used to # in
Macro-32).

So I cannot evaluate the quality of that article.

I just considered it slightly relevant as I know there are people her
that actually have used a PDP-11.

Arne

On 3/14/22 20:21, Arne Vajhøj wrote:
> On 3/14/2022 8:17 PM, Bob Gezelter wrote:
>> On Monday, March 14, 2022 at 7:47:34 PM UTC-4, Arne Vajhøj wrote:
>>> https://arstechnica.com/gadgets/2022/03/a-brief-tour-of-the-pdp-11-the-most-influential-minicomputer-of-all-time/
>>>
>>
>> Not sure where the author of the arstechnica piece saw "$" for
>> immediate mode, e.g., mov $10,r0. MACRO-11 as I new it, always used a
>> "#", e.g., MOV #SS.XYZ,R0.
>>
>> Spent lots of time writing and generating assembler for RSX-11 systems
>> and relatives, e.g., P/OS. Did many interesting things.
>
> I have never used a PDP-11 so I have no idea (I am used to # in
> Macro-32).
>
> So I cannot evaluate the quality of that article.
>
> I just considered it slightly relevant as I know there are people her
> that actually have used a PDP-11.

Not only have, but still do. :-)

In MACRO-11 its #, not $.

bill

On 2022-03-14, Bob Gezelter <gezelter@rlgsc.com> wrote:
> On Monday, March 14, 2022 at 7:47:34 PM UTC-4, Arne Vajhøj wrote:
>> https://arstechnica.com/gadgets/2022/03/a-brief-tour-of-the-pdp-11-the-most-influential-minicomputer-of-all-time/
> Arne,
>
> Not sure where the author of the arstechnica piece saw "$" for immediate mode, e.g., mov $10,r0. MACRO-11 as I new it, always used a "#", e.g., MOV #SS.XYZ,R0.
>
> Spent lots of time writing and generating assembler for RSX-11 systems and relatives, e.g., P/OS. Did many interesting things.
>
> - Bob Gezelter, http://www.rlgsc.com

DEC versus AT&T syntax (and yes, I know the following is Intel not DEC,
but it's much the same thing here for the syntax you mention):

https://wiki.osdev.org/Opcode_syntax

Perfectly normal and expected. Also note "mov src, dest" instead of
"mov dest, src".

Expect to see more of it in your future. :-)

Simon.

--
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.

On 2022-03-14, Arne Vajhøj <arne@vajhoej.dk> wrote:
> On 3/14/2022 8:17 PM, Bob Gezelter wrote:
>> On Monday, March 14, 2022 at 7:47:34 PM UTC-4, Arne Vajhøj wrote:
>>> https://arstechnica.com/gadgets/2022/03/a-brief-tour-of-the-pdp-11-the-most-influential-minicomputer-of-all-time/
>>
>> Not sure where the author of the arstechnica piece saw "$" for immediate mode, e.g., mov $10,r0. MACRO-11 as I new it, always used a "#", e.g., MOV #SS.XYZ,R0.
>>
>> Spent lots of time writing and generating assembler for RSX-11 systems and relatives, e.g., P/OS. Did many interesting things.
>
> I have never used a PDP-11 so I have no idea (I am used to # in
> Macro-32).
>

Unix generally uses AT&T syntax. The syntax is expected (and looks
perfectly normal to me) if the author is playing with Unix on a PDP-11.

Simon.

--
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.

On 03/15/22 01:22, Simon Clubley wrote:
> On 2022-03-14, Bob Gezelter<gezelter@rlgsc.com> wrote:
>> On Monday, March 14, 2022 at 7:47:34 PM UTC-4, Arne Vajhøj wrote:
>>> https://arstechnica.com/gadgets/2022/03/a-brief-tour-of-the-pdp-11-the-most-influential-minicomputer-of-all-time/
>> Arne,
>>
>> Not sure where the author of the arstechnica piece saw "$" for immediate mode, e.g., mov $10,r0. MACRO-11 as I new it, always used a "#", e.g., MOV #SS.XYZ,R0.
>>
>> Spent lots of time writing and generating assembler for RSX-11 systems and relatives, e.g., P/OS. Did many interesting things.
>>
>> - Bob Gezelter, http://www.rlgsc.com
>
> DEC versus AT&T syntax (and yes, I know the following is Intel not DEC,
> but it's much the same thing here for the syntax you mention):
>
> https://wiki.osdev.org/Opcode_syntax
>
> Perfectly normal and expected. Also note "mov src, dest" instead of
> "mov dest, src".

Yes, from, to, left to right. Same for 68000 series as well. Intel
always were a bit backward in that respect...

Chris

>
> Expect to see more of it in your future. :-)

>
> Simon.
>

chris <chris-nospam@tridac.net> writes:

> On 03/15/22 01:22, Simon Clubley wrote:
>> On 2022-03-14, Bob Gezelter<gezelter@rlgsc.com> wrote:
>>> On Monday, March 14, 2022 at 7:47:34 PM UTC-4, Arne Vajh�j wrote:
>>>> https://arstechnica.com/gadgets/2022/03/a-brief-tour-of-the-pdp-11-the-most-influential-minicomputer-of-all-time/

>>> Arne,

>>> Not sure where the author of the arstechnica piece saw "$" for immediate
>>> mode, e.g., mov $10,r0. MACRO-11 as I new it, always used a "#", e.g., MOV
>>> #SS.XYZ,R0.

>>> Spent lots of time writing and generating assembler for RSX-11 systems and
>>> relatives, e.g., P/OS. Did many interesting things.

>>> - Bob Gezelter, http://www.rlgsc.com

>> DEC versus AT&T syntax (and yes, I know the following is Intel not DEC,
>> but it's much the same thing here for the syntax you mention):

>> https://wiki.osdev.org/Opcode_syntax

>> Perfectly normal and expected. Also note "mov src, dest" instead of
>> "mov dest, src".

> Yes, from, to, left to right. Same for 68000 series as well. Intel
> always were a bit backward in that respect...

>> Expect to see more of it in your future. :-)

"DEC" syntax, hmm? Macro-10:

MOVE 17,SUMWHR
ADDI 17,37
MOVEM 17,ELSWHR

The "destination" AC always follows the opcode immediately, the effective
address of the "source" comes after the comma. Note that since there are
"to-memory" instructions, the notion of "source" vs. "destination" is not
particularly useful...

--
Rich Alderson news@alderson.users.panix.com
Audendum est, et veritas investiganda; quam etiamsi non assequamur,
omnino tamen proprius, quam nunc sumus, ad eam perveniemus.
--Galen

On 3/14/22 21:22, Simon Clubley wrote:
> On 2022-03-14, Bob Gezelter <gezelter@rlgsc.com> wrote:
>> On Monday, March 14, 2022 at 7:47:34 PM UTC-4, Arne Vajhøj wrote:
>>> https://arstechnica.com/gadgets/2022/03/a-brief-tour-of-the-pdp-11-the-most-influential-minicomputer-of-all-time/
>> Arne,
>>
>> Not sure where the author of the arstechnica piece saw "$" for immediate mode, e.g., mov $10,r0. MACRO-11 as I new it, always used a "#", e.g., MOV #SS.XYZ,R0.
>>
>> Spent lots of time writing and generating assembler for RSX-11 systems and relatives, e.g., P/OS. Did many interesting things.
>>
>> - Bob Gezelter, http://www.rlgsc.com
>
> DEC versus AT&T syntax (and yes, I know the following is Intel not DEC,
> but it's much the same thing here for the syntax you mention):
>

That appears to be it. Just checked again and see that under Ultrix-11
it is the "$" instead of the "#" and we all now that Ultrix-11 is really
just V7 warmed over. :-)

bill

On 03/15/22 02:18, Rich Alderson wrote:
> chris<chris-nospam@tridac.net> writes:
>
>> On 03/15/22 01:22, Simon Clubley wrote:
>>> On 2022-03-14, Bob Gezelter<gezelter@rlgsc.com> wrote:
>>>> On Monday, March 14, 2022 at 7:47:34 PM UTC-4, Arne Vajhøj wrote:
>>>>> https://arstechnica.com/gadgets/2022/03/a-brief-tour-of-the-pdp-11-the-most-influential-minicomputer-of-all-time/
>
>>>> Arne,
>
>>>> Not sure where the author of the arstechnica piece saw "$" for immediate
>>>> mode, e.g., mov $10,r0. MACRO-11 as I new it, always used a "#", e.g., MOV
>>>> #SS.XYZ,R0.
>
>>>> Spent lots of time writing and generating assembler for RSX-11 systems and
>>>> relatives, e.g., P/OS. Did many interesting things.
>
>>>> - Bob Gezelter, http://www.rlgsc.com
>
>>> DEC versus AT&T syntax (and yes, I know the following is Intel not DEC,
>>> but it's much the same thing here for the syntax you mention):
>
>>> https://wiki.osdev.org/Opcode_syntax
>
>>> Perfectly normal and expected. Also note "mov src, dest" instead of
>>> "mov dest, src".
>
>> Yes, from, to, left to right. Same for 68000 series as well. Intel
>> always were a bit backward in that respect...
>
>>> Expect to see more of it in your future. :-)
>
> "DEC" syntax, hmm? Macro-10:
>
> MOVE 17,SUMWHR
> ADDI 17,37
> MOVEM 17,ELSWHR
>
> The "destination" AC always follows the opcode immediately, the effective
> address of the "source" comes after the comma. Note that since there are
> "to-memory" instructions, the notion of "source" vs. "destination" is not
> particularly useful...
>

Perhaps, but people no longer program in octal, nor have to worry about
where the opcode field etc is in the instruction stream. Not familiar
with Macro-10 syntax, but assume that would be source -> destination as
well.

Just saying, read left to right, move something from a source to a
destination, so the dec pdp11 macro syntax is more natural. Having
worked with a lot of micros, some of which are quite primitive and
badly thought out, the PDP11 was light years ahead. Instructions
like sob, to create a tight loop in 3 lines of macro were truly
revolutionary and being of the sixties, always wondered what
those guys must have been smoking...

Chris

On Monday, March 14, 2022 at 7:18:27 PM UTC-7, Rich Alderson wrote:
>
(snip of DEC syntax)

> "DEC" syntax, hmm? Macro-10:
> MOVE 17,SUMWHR
> ADDI 17,37
> MOVEM 17,ELSWHR
> The "destination" AC always follows the opcode immediately, the effective
> address of the "source" comes after the comma. Note that since there are
> "to-memory" instructions, the notion of "source" vs. "destination" is not
> particularly useful...
For IBM S/360 and successors, it is right to left, except for store instuctions,
which usually (or always) have opcodes starting with ST. That makes them
easy to recognize.

PDP-10 "to-memory" instructions are not so easy to recognize.

On Wed, 16 Mar 2022 00:25:47 +0000, chris wrote:

> Just saying, read left to right, move something from a source to a
> destination, so the dec pdp11 macro syntax is more natural.

But possibly counter intuitive to a high level programmer, who is uwsed
to assignments going right to left!

One of my favourite architectures was single address, so no problem
anyway.

--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

On 2022-03-16 01:25, chris wrote:
> On 03/15/22 02:18, Rich Alderson wrote:
>> chris<chris-nospam@tridac.net>  writes:
>>
>>> On 03/15/22 01:22, Simon Clubley wrote:
>>>> On 2022-03-14, Bob Gezelter<gezelter@rlgsc.com>   wrote:
>>>>> On Monday, March 14, 2022 at 7:47:34 PM UTC-4, Arne Vajhøj wrote:
>>>>>> https://arstechnica.com/gadgets/2022/03/a-brief-tour-of-the-pdp-11-the-most-influential-minicomputer-of-all-time/
>>>>>>
>>
>>>>> Arne,
>>
>>>>> Not sure where the author of the arstechnica piece saw "$" for
>>>>> immediate
>>>>> mode, e.g., mov $10,r0. MACRO-11 as I new it, always used a "#",
>>>>> e.g., MOV
>>>>> #SS.XYZ,R0.
>>
>>>>> Spent lots of time writing and generating assembler for RSX-11
>>>>> systems and
>>>>> relatives, e.g., P/OS. Did many interesting things.
>>
>>>>> - Bob Gezelter, http://www.rlgsc.com
>>
>>>> DEC versus AT&T syntax (and yes, I know the following is Intel not DEC,
>>>> but it's much the same thing here for the syntax you mention):
>>
>>>> https://wiki.osdev.org/Opcode_syntax

The article is actually mixing Unix and DEC notations wildly, as well as
having various errors in there.

>>>> Perfectly normal and expected. Also note "mov src, dest" instead of
>>>> "mov dest, src".
>>
>>> Yes, from, to, left to right. Same for 68000 series as well. Intel
>>> always were a bit backward in that respect...
>>
>>>> Expect to see more of it in your future. :-)
>>
>> "DEC" syntax, hmm?  Macro-10:
>>
>>     MOVE 17,SUMWHR
>>     ADDI 17,37
>>     MOVEM 17,ELSWHR
>>
>> The "destination" AC always follows the opcode immediately, the effective
>> address of the "source" comes after the comma.  Note that since there are
>> "to-memory" instructions, the notion of "source" vs. "destination" is not
>> particularly useful...

This is one of the things I most dislike about Macro-10 actually. :-D

> Perhaps, but people no longer program in octal, nor have to worry about
> where the opcode field etc is in the instruction stream. Not familiar
> with Macro-10 syntax, but assume that would be source -> destination as
> well.

That's what "MOVE" vs. "MOVEM" is. MOVE moves from memory, MOVEM moves
to memory. But arguments are always "accumulator,address", independent
of which direction data goes.

> Just saying, read left to right, move something from a source to a
> destination, so the dec pdp11 macro syntax is more natural. Having
> worked with a lot of micros, some of which are quite primitive and
> badly thought out, the PDP11 was light years ahead. Instructions
> like sob, to create a tight loop in 3 lines of macro were truly
> revolutionary and being of the sixties, always wondered what
> those guys must have been smoking...

Yes, Macro-11 is rather natural. And *very* much like Macro-32.
However, SOB was not in the original instruction set of the PDP-11. It's
an extension.

But why 3 lines of macro? For many things, it's just 2...

10$: MOV (R0)+,(R1)+
SOB R2,10$

Johnny

gah4 <gah4@u.washington.edu> writes:

> On Monday, March 14, 2022 at 7:18:27 PM UTC-7, Rich Alderson wrote:

> (snip of DEC syntax)

>> "DEC" syntax, hmm? Macro-10:

>> MOVE 17,SUMWHR
>> ADDI 17,37
>> MOVEM 17,ELSWHR

>> The "destination" AC always follows the opcode immediately, the effective
>> address of the "source" comes after the comma. Note that since there are
>> "to-memory" instructions, the notion of "source" vs. "destination" is not
>> particularly useful...

> For IBM S/360 and successors, it is right to left, except for store instuctions,
> which usually (or always) have opcodes starting with ST. That makes them
> easy to recognize.

> PDP-10 "to-memory" instructions are not so easy to recognize.

Nonsense.

ALL the PDP-10 mnemonics for instructions which access memory have the same
form (taking MOVE as a canonical example):

MOVE load accumulator with contents of memory at effective address
MOVEI load accumulator with immediate effective address calculation
MOVES load accumulator with swapped halfwords of contents of memory
at effective address
MOVEM store accumulator into memory at effective address

Look at the last character of the instruction. You don't even have to remember
the difference between "load" and "store".

--
Rich Alderson news@alderson.users.panix.com
Audendum est, et veritas investiganda; quam etiamsi non assequamur,
omnino tamen proprius, quam nunc sumus, ad eam perveniemus.
--Galen

On 03/16/22 18:30, Johnny Billquist wrote:
> On 2022-03-16 01:25, chris wrote:
>> On 03/15/22 02:18, Rich Alderson wrote:
>>> chris<chris-nospam@tridac.net> writes:
>>>
>>>> On 03/15/22 01:22, Simon Clubley wrote:
>>>>> On 2022-03-14, Bob Gezelter<gezelter@rlgsc.com> wrote:
>>>>>> On Monday, March 14, 2022 at 7:47:34 PM UTC-4, Arne Vajhøj wrote:
>>>>>>> https://arstechnica.com/gadgets/2022/03/a-brief-tour-of-the-pdp-11-the-most-influential-minicomputer-of-all-time/
>>>>>>>
>>>
>>>>>> Arne,
>>>
>>>>>> Not sure where the author of the arstechnica piece saw "$" for
>>>>>> immediate
>>>>>> mode, e.g., mov $10,r0. MACRO-11 as I new it, always used a "#",
>>>>>> e.g., MOV
>>>>>> #SS.XYZ,R0.
>>>
>>>>>> Spent lots of time writing and generating assembler for RSX-11
>>>>>> systems and
>>>>>> relatives, e.g., P/OS. Did many interesting things.
>>>
>>>>>> - Bob Gezelter, http://www.rlgsc.com
>>>
>>>>> DEC versus AT&T syntax (and yes, I know the following is Intel not
>>>>> DEC,
>>>>> but it's much the same thing here for the syntax you mention):
>>>
>>>>> https://wiki.osdev.org/Opcode_syntax
>
> The article is actually mixing Unix and DEC notations wildly, as well as
> having various errors in there.
>
>>>>> Perfectly normal and expected. Also note "mov src, dest" instead of
>>>>> "mov dest, src".
>>>
>>>> Yes, from, to, left to right. Same for 68000 series as well. Intel
>>>> always were a bit backward in that respect...
>>>
>>>>> Expect to see more of it in your future. :-)
>>>
>>> "DEC" syntax, hmm? Macro-10:
>>>
>>> MOVE 17,SUMWHR
>>> ADDI 17,37
>>> MOVEM 17,ELSWHR
>>>
>>> The "destination" AC always follows the opcode immediately, the
>>> effective
>>> address of the "source" comes after the comma. Note that since there
>>> are
>>> "to-memory" instructions, the notion of "source" vs. "destination" is
>>> not
>>> particularly useful...
>
> This is one of the things I most dislike about Macro-10 actually. :-D
>
>> Perhaps, but people no longer program in octal, nor have to worry about
>> where the opcode field etc is in the instruction stream. Not familiar
>> with Macro-10 syntax, but assume that would be source -> destination as
>> well.
>
> That's what "MOVE" vs. "MOVEM" is. MOVE moves from memory, MOVEM moves
> to memory. But arguments are always "accumulator,address", independent
> of which direction data goes.
>

Quite similar to some 8 bit micro architecture, where everything is
relative to either the accumulator or an index register. No concept
of source or destination as in pdp11 and others. Data General Nova
was an accumulator / index register machine as well, vastly inferior
to the pdp11.

>> Just saying, read left to right, move something from a source to a
>> destination, so the dec pdp11 macro syntax is more natural. Having
>> worked with a lot of micros, some of which are quite primitive and
>> badly thought out, the PDP11 was light years ahead. Instructions
>> like sob, to create a tight loop in 3 lines of macro were truly
>> revolutionary and being of the sixties, always wondered what
>> those guys must have been smoking...
>
> Yes, Macro-11 is rather natural. And *very* much like Macro-32.
> However, SOB was not in the original instruction set of the PDP-11. It's
> an extension.
>
> But why 3 lines of macro? For many things, it's just 2...
>
> 10$: MOV (R0)+,(R1)+
> SOB R2,10$
>
> Johnny

Yes the basic loop is just 2 lines, ignoring initialisation, but the
point is that that instruction was pretty high level for a machine
that must have been designed around 1968.

Do have the 1970 11/05 and 11/10 handbook and it was just the those
two that lacked the sob instruction. Used it all the time here and yes,
nearly always the same registers for variables, loop counters, addresses
etc...

Chris

On 03/16/22 09:28, Bob Eager wrote:
> On Wed, 16 Mar 2022 00:25:47 +0000, chris wrote:
>
>> Just saying, read left to right, move something from a source to a
>> destination, so the dec pdp11 macro syntax is more natural.
>
> But possibly counter intuitive to a high level programmer, who is used
> to assignments going right to left!

Programmed in C for years as well, but perhaps different mental
processes for asm vs high level language programming ?. Assembler
is primarily moving something to work on,. whereas hll is more
algebraic by design and follows such rules.

Perhaps it's partly a matter of what we become familiar with though...

Chris

>
> One of my favourite architectures was single address, so no problem
> anyway.
>
>
>

On Thu, 17 Mar 2022 00:16:35 +0000, chris wrote:

> On 03/16/22 09:28, Bob Eager wrote:
>> On Wed, 16 Mar 2022 00:25:47 +0000, chris wrote:
>>
>>> Just saying, read left to right, move something from a source to a
>>> destination, so the dec pdp11 macro syntax is more natural.
>>
>> But possibly counter intuitive to a high level programmer, who is used
>> to assignments going right to left!
>
> Programmed in C for years as well, but perhaps different mental
> processes for asm vs high level language programming ?. Assembler is
> primarily moving something to work on,. whereas hll is more algebraic by
> design and follows such rules.

I did some programming in POP_2 once:

https://en.wikipedia.org/wiki/POP-2

Assignments are left to right! But one of the few examples in languages
(have used (incl. FORTRAN, Algol, BASIC, Pascal, C, C++, BCPL, etc.).
Assemblers are very inconsistent; I have used DEC syntax (PDP-11, VAX),
AT&T syntax (PDP-11, VAX), and also DEC syntax (PDP-10) which, as already
noted, is all about having the accumulator on the left regardless of the
direction of travel.

And then there's LISP...

--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

On Thu, 17 Mar 2022 00:07:07 +0000, chris wrote:

> Yes the basic loop is just 2 lines, ignoring initialisation, but the
> point is that that instruction was pretty high level for a machine that
> must have been designed around 1968.
>
> Do have the 1970 11/05 and 11/10 handbook and it was just the those two
> that lacked the sob instruction.

11/20 didn't have it either. Very early PDP-11, and my first one.
I think there were others...I have a pretty complete set of handbooks
here but it's not worth poring through them!
--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

On 2022-03-16, Rich Alderson <news@alderson.users.panix.com> wrote:
>
> ALL the PDP-10 mnemonics for instructions which access memory have the same
> form (taking MOVE as a canonical example):
>
> MOVE load accumulator with contents of memory at effective address
> MOVEI load accumulator with immediate effective address calculation
> MOVES load accumulator with swapped halfwords of contents of memory
> at effective address
> MOVEM store accumulator into memory at effective address
>
> Look at the last character of the instruction. You don't even have to remember
> the difference between "load" and "store".
>

Doesn't anyone else find it strange that the mnemonic across all
architectures is some variant of MOVE or MOV instead of COPY or CPY ?

After all, you are not destroying the contents at the original
location/register when you copy it to the target location/register. :-)

Simon.

--
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.

On Wednesday, March 16, 2022 at 5:48:43 PM UTC-7, Simon Clubley wrote:

(snip)

> Doesn't anyone else find it strange that the mnemonic across all
> architectures is some variant of MOVE or MOV instead of COPY or CPY ?
> After all, you are not destroying the contents at the original
> location/register when you copy it to the target location/register. :-)

I think I might have wondered about that.

C has the memmove() and memcpy() functions, where the former does
it correctly (for some definition of correct) for overlapping areas.
memcpy() gives undefined results in that case.

The S/360 MVC (move characters) is defined to do the move left to
right, character by character, in the case of overlap. This is commonly
used to clear a buffer by storing a character in the first byte, and then
moving right by one.

It is done enough that some hardware might optimize for this case.

I suspect that opcodes for many later processors were based, in some
sense, on earlier DEC systems.

But yes, it is strange.

On Thu, 17 Mar 2022 00:48:41 +0000, Simon Clubley wrote:

> On 2022-03-16, Rich Alderson <news@alderson.users.panix.com> wrote:
>>
>> ALL the PDP-10 mnemonics for instructions which access memory have the
>> same form (taking MOVE as a canonical example):
>>
>> MOVE load accumulator with contents of memory at effective
address
>> MOVEI load accumulator with immediate effective address
calculation
>> MOVES load accumulator with swapped halfwords of contents of
memory
>> at effective address
>> MOVEM store accumulator into memory at effective address
>>
>> Look at the last character of the instruction. You don't even have to
>> remember the difference between "load" and "store".
>>
>>
> Doesn't anyone else find it strange that the mnemonic across all
> architectures is some variant of MOVE or MOV instead of COPY or CPY ?
>
> After all, you are not destroying the contents at the original
> location/register when you copy it to the target location/register.

And then you have the PDP-8, which doesn't have MOVE. But DCA clears the
accumulator when copying its contents.

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In article <t0u0h9$839$1@dont-email.me>, Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP> writes:
>On 2022-03-16, Rich Alderson <news@alderson.users.panix.com> wrote:
>>
>> ALL the PDP-10 mnemonics for instructions which access memory have the same
>> form (taking MOVE as a canonical example):
>>
>> MOVE load accumulator with contents of memory at effective address
>> MOVEI load accumulator with immediate effective address calculation
>> MOVES load accumulator with swapped halfwords of contents of memory
>> at effective address
>> MOVEM store accumulator into memory at effective address
>>
>> Look at the last character of the instruction. You don't even have to remember
>> the difference between "load" and "store".
>>
>
>Doesn't anyone else find it strange that the mnemonic across all
>architectures is some variant of MOVE or MOV instead of COPY or CPY ?
>
>After all, you are not destroying the contents at the original
>location/register when you copy it to the target location/register. :-)

But you have no misgiving about 'cd'?

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I speak to machines with the voice of humanity.

On Wednesday, March 16, 2022 at 8:48:43 PM UTC-4, Simon Clubley wrote:
> On 2022-03-16, Rich Alderson <ne...@alderson.users.panix.com> wrote:
> >
> > ALL the PDP-10 mnemonics for instructions which access memory have the same
> > form (taking MOVE as a canonical example):
> >
> > MOVE load accumulator with contents of memory at effective address
> > MOVEI load accumulator with immediate effective address calculation
> > MOVES load accumulator with swapped halfwords of contents of memory
> > at effective address
> > MOVEM store accumulator into memory at effective address
> >
> > Look at the last character of the instruction. You don't even have to remember
> > the difference between "load" and "store".
> >
> Doesn't anyone else find it strange that the mnemonic across all
> architectures is some variant of MOVE or MOV instead of COPY or CPY ?
>

Alpha has neither. The assembler has a pseudo-op named MOV but that is just a
OR with R0

On 2022-03-17, VAXman- @SendSpamHere.ORG <VAXman-@SendSpamHere.ORG> wrote:
> In article <t0u0h9$839$1@dont-email.me>, Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP> writes:
>>
>>Doesn't anyone else find it strange that the mnemonic across all
>>architectures is some variant of MOVE or MOV instead of COPY or CPY ?
>>
>>After all, you are not destroying the contents at the original
>>location/register when you copy it to the target location/register. :-)
>
> But you have no misgiving about 'cd'?
>

Shell command "cd" ? Interesting observation.

OTOH, shells have both move/mv and copy/cp commands, which do exactly
what they say.

Simon.

--
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
Walking destinations on a map are further away than they appear.

On 2022-03-17 01:48, Simon Clubley wrote:
> On 2022-03-16, Rich Alderson <news@alderson.users.panix.com> wrote:
>>
>> ALL the PDP-10 mnemonics for instructions which access memory have the same
>> form (taking MOVE as a canonical example):
>>
>> MOVE load accumulator with contents of memory at effective address
>> MOVEI load accumulator with immediate effective address calculation
>> MOVES load accumulator with swapped halfwords of contents of memory
>> at effective address
>> MOVEM store accumulator into memory at effective address
>>
>> Look at the last character of the instruction. You don't even have to remember
>> the difference between "load" and "store".
>>
>
> Doesn't anyone else find it strange that the mnemonic across all
> architectures is some variant of MOVE or MOV instead of COPY or CPY ?

You mean across all of these two (or three) DEC architectures (PDP-10,
PDP-11 and VAX)?

Because some others use LOAD, LD, or some variant thereof. And then you
have (as mentioned) the PDP-8 which only have TAD (two complement add),
so if you want to read something out of memory, you better make sure the
AC is 0 before you do. Which of course is helped by the store
instruction which implicitly also clears the AC (DCA - Deposit and Clear
AC).
And there are other things out there as well, if we talk about "all
architectures".

Johnny