New CP/M 2.2 implelentation for 16FDC and 64FDC

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Martin Eberhard

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Jun 3, 2021, 11:19:20 PM6/3/21
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I've just released a new CP/M implementation for Cromemco machines.

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.

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.

Richard Deane

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Jun 4, 2021, 6:15:15 AM6/4/21
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Sounds good  but for those of us without a real Cromemco, I wish there was an fpga implementation.
Richard 

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Emil Sarlija

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Jun 4, 2021, 6:36:27 AM6/4/21
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Hi Richard,

You can emulate a Cromemco system in simh with the altairz80 simulator. I'll probably use it to attempt to build this before putting it on physical media for my real Cromemco.

Martin - this is exciting stuff. Thanks for your efforts.

Thanks,
Emil

Richard Deane

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Jun 4, 2021, 7:20:13 AM6/4/21
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Thanks for the info. I hope you can post the simh altairz80 config when you get it all set up. I am familiar with altairz80, but only used it as plain z80 cp/m. Great piece of software from Peter Schorn.

cro memcos

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Jun 4, 2021, 8:30:39 AM6/4/21
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Wow!    I've just began to look at the documentation link   i.e.


Very impressive.    I  do feel good documentation is a lost art these days.

I will take the code and try it on a physical and virtual system and report back.

Emil Sarlija

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Jun 11, 2021, 8:38:36 PM6/11/21
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Hi all,

If anyone is able to make an IMD image of a running system on an 8" DSDD floppy, please let me know.

Many thanks,
Emil

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