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devel / comp.os.cpm / New CP/M implementation for Cromemco machines

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o New CP/M implementation for Cromemco machinesMartin Eberhard

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New CP/M implementation for Cromemco machines

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Subject: New CP/M implementation for Cromemco machines
From: mfeberh...@gmail.com (Martin Eberhard)
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 by: Martin Eberhard - Fri, 4 Jun 2021 03:25 UTC

Sorry for the cross-posting for those of you who also read comp.os.cromemco!

I've just released a new CP/M implementation for Cromemco machines with either the 16FDC or 64FDC disk controller.

The BIOS buffers an entire floppy disk track, using a separate bank of RAM, making accesses super fast. (And this is an excellent use of an old 16KZ DRAM board, once you have switched to a 64KZ... Or you can use another 64KZ....)

Because the track buffer is in its own memory page, this is a tight BIOS, allowing for a 63K CP/M build. (If you want, you can assemble the code to place the track buffer in main memory, but this will consume an additional 10K of RAM.)

The BIOS automatically detects and configures itself for pretty much any type of floppy drive, or any combination of:

* 2SDD 80-track 3.5" drives, 256, 512, or 1024 bytes/sector
* 5.25" 40-track drives, 1SSD, 1SDD, 2SSD, 2SDD, all possible sector sizes
* 5.25" 80-track, 2SDD "quad density" drives, 256, 512, or 1024 bytes/sector
* 5.25" 80-track 2SDD "high density" drives, 256, 512, or 1024 bytes/sector
* 8" 77-track drives, 1SSD, 1SDD, 2SSD, 2SDD, all possible sector sizes
* PerSci 277 and 290 "voicecoil" drives, same formats as other 8" drives

Along with CroBIOS, I have written:

* CroBoot, boot code that's compatible with the RDOS PROM on the disk controller
* CroForm, a disk formatter for all the above drive types
CroGen, a SYSGEN for the Cromemco disk controllers that also formats the system tracks
* CroFlex, a floppy disk exerciser for debugging and tuning floppy drives
* Reboot, a simple command to cause a cold boot from floppy

If you are interested, you can find documentation and code here:

https://deramp.com/downloads/mfe_archive/005-Documentation%20and%20Code%20by%20Martin/010%20Code%20by%20Martin/CPM%20Code/Cromemco/

The source code is extensively commented, especially the BIOS source. These comments include guidance for how to set up the jumpers and switches for the ZPU, the 16FDC or 64FDC, the main memory board (64KZ or 64KZ-II), the track buffer memory board (16KZ, 64KZ, or 64KZ-II), the TU-ART, and the PRI, if you choose to use one.

Your feedback is encouraged :-)

Martin E.

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