WTB 16KZ DRAM Board for CP/M BIOS Build

Jim McClanahan

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Mar 1, 2024, 11:40:24 AMMar 1

to crom...@googlegroups.com

I am soon to be retired and one of the first vintage computer projects that I've been looking forward to is getting Martin Eberhard's CP/M BIOS going on my Cromemco Z-2D.

If anyone has a 16KZ memory card (or two) they are interested in selling, I would be interested in buying.

Building and getting a BIOS running from source has always been something that interested me, but that I've never had the time to do. Right now I'm running the Z-2D with CP/M on two 3.5" drives that look like a pair of 8" drives to the system. (I'm going to have to dig back into my notes on what was involved in that. I think I just had to find drives that I could strap to run at 360 RPM vs. the normal 300 RPM (or visa versa). I also just lived with 73 tracks because I never was able to successfully patch things to access all 80. So the system really pretty much treats them as normal 8" floppy drives.)

Thanks,

Jim W4JBM

"With a soldering iron in one hand, a schematic in the other, and a puzzled look on his face…"

Peter Higgins

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Mar 1, 2024, 12:07:12 PMMar 1

to Cromemco

There are several 16KZ boards currently listed on eBay at fairly low prices, since there is not much interest in them.

If the goal is to run CP/M (and not Cromemco Z80 Cromix) why not just get a basic 64K static RAM board ?

Martin Eberhard

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Mar 1, 2024, 12:55:02 PMMar 1

to Cromemco

My BIOS does whole-track buffering to make it extremely fast. So as not to waste main memory, it uses a second page of RAM for the track buffer. this is a great way to use an otherwise not very useful 16KZ. (You could use a 64KZ or other RAM board with Cromemco-compatible bank-switching, but the track buffer fits in 16K, even with the most dense floppy drives.)

This BIOS also auto-detects between most kinds of floppy drives 8", 5.25", 3.5", SD or DD (or Quad-Density in the case of 5.25" drives), 1S or 2S, and supports both Shugart-style and PerSci -style 8" drives.

See here for the BIOS source, as well as additional documentation. You might find the drive identification flowchart interesting... :

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

-Martin

Martin Eberhard

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Mar 1, 2024, 12:58:46 PMMar 1

to Cromemco

Other useful related programs (such as Boot and Format) here:

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

-Martin

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