Junkbox CP/M system?

Jules Richardson julesrichardsonuk at yahoo.co.uk
Mon Apr 23 18:47:34 CDT 2007

Chuck Guzis wrote:
> On 23 Apr 2007 at 11:23, Allison wrote:
>> To run CP/M you don't need a lot but the minimal and useful complete 
>> system are not far apart.
>> Z80: Whatever you have! 
>> RAM: 48-64k of ram 48k will be enough to run a lot of software, but 64k
>> is only 2 61256s (a 32kx8 SRAM).  CP/M will run in 32k but limited 
>> application software will fit.  The only requirement is ram starts at 
>> 0000h and be contigious for at least 20K(minimum) after boot.
> If I were to approach a project like this, I'd probably go find an 
> old junker credit-card or POS terminal ...

Wouldn't it take a fair while to reverse-engineer all the address decoding and 
additional logic (such as for driving the LCD) in the system? i.e. just to 
find out exactly what you have in order to start thinking about writing 
software is reasonably non-trivial.

It's probably nothing like as much as designing/building something from 
scratch, but then at least with doing something from scratch there's the 
benefit of knowing exactly how it fits together. Plus I suspect for many 
people, designing from a box of chips ends up being more rewarding...

> Most of these things have lots of SRAM (128-512K) 

Hmm, do they? I passed up on some '386 ones recently (I was briefly tempted 
mainly for the 40x2 displays). Some more SRAM would have been nice to have, 

> Just buffer some data and address lines off for a floppy or IDE 
 > interface

 From a programming point of view, how easy is accessing IDE compared to a 
typical FDC ('765 or similar)? I did write some assembler to access an IDE 
drive about 12 years ago, but have long since forgotten details! :-)

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