24 Apr
2007
24 Apr
'07
12:47 a.m.
Chuck Guzis wrote:
On 23 Apr 2007 at 11:23, Allison wrote:
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...
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 ... 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,
though...
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! :-)