Unknown S100 system

Roy J. Tellason rtellason at verizon.net
Fri Sep 21 15:35:41 CDT 2007


On Friday 21 September 2007 16:01, Chuck Guzis wrote:
> On 21 Sep 2007 at 14:07, Roy J. Tellason wrote:
> > I wonder why they went with that part?  I seem to remember some others
> > that used it as well,  though specifics are not coming to mind at the
> > moment.  I have a bunch of those on hand,  and think about doing
> > something with them from time to time.  It's a fairly easy chip to use, 
> > with an eprom and a ram chip and a single address latch,  I just haven't
> > decided yet what I'm gonna do with it.
>
> Compupro 85/88 board; my own Durango F-85 and a host of others.  If
> you can find some of the support chips (8155, 8755), the parts count
> can be very low, given the vintage of the 8085.

Compupro was the one that was hanging out there at the edge of recall...

I may have some of those support chips,  too.  8155 (and 8156,  which is the 
same part with a different select pin polarity if I'm remembering right) 
sound real familiar.  I have the 8085 Cookbook and a few others that Sams put 
out,  one covering this text editor and assembler (which I didn't really care 
for,  but...).  No interest in the ROM-based 8355 and I've never seen the 
EPROM-based 8755.  The relative i/o and RAM address mapping of those parts 
gets a little confusing,  though,  and the book is a bit less clear than it 
could be on that aspect of it.

> I suspect that the reason 8088/8085 pairs were fairly common in
> comparison to Z80/8088 pairs was that timings and buses on the 8088
> and 8085 are *very* similar and getting them to work with 8000-series
> peripherals was very easy.  IIRC, one could even replace an 8085 with
> an 8088 (assuming you were restricting it to 64K addressing) with a
> minimum of "glue".  Both multiplex the data lines on A0-A7 the same
> way.

Ah.

I'd never really looked at the 8088 and later parts all that much,  or to that 
level of detail.

> I suspect it might be easier to substitute an NSC800 for an 8085 if
> Z80 functionality is needed than trying to shoehorn in a Z80.

That's another part I have no familiarity with at all at this point in time,  
though of course I've heard of it.

With regard to what little programming I've done,  the thing I like most about 
the z80 is relative jumps,  which makes relocatable code easy to do.  The 
other big deal is the alternate register set and the index registers,  which 
I really haven't used all that much.

-- 
Member of the toughest, meanest, deadliest, most unrelenting -- and
ablest -- form of life in this section of space,  a critter that can
be killed but can't be tamed.  --Robert A. Heinlein, "The Puppet Masters"
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Information is more dangerous than cannon to a society ruled by lies. --James 
M Dakin




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