Heath h-8 - test-drb@ccmp.vtda.org

20 Dec 2001

...
  -----Original Message-----
 From: ard(a)p850ug1.demon.co.uk [mailto:ard@p850ug1.demon.co.uk] 
...
   So, how rare
are the peripherals?  In the absence of a   heath floppy drive,
 > what else might I use(and how...)?  Anyone know where I can get one? 
...
  The H17 should be able to use any normal 5.25"
floppy drive.
 The Heathkit
 ones were (IIRC) 40 cylinder single sided. I would suspect
 you could link
 up a PC 360K drive and get it to work. You might have to cut the
 connection to the side select pin (which will then be pulled
 high by the
 termiating resistors in the drive) so that it behaves as a
 single-sided
 unit. And there may be some issue with the drive select pins. But it
 should be possible to get it to work. 
So hard sectors aren't required, then?
I don't have a cable for it yet, so I'll just have to plan on cutting a
wire. :)
...
  If you have such a drive and a PSU to run it off,
I'll dig
 out the H17
 schematic (it's used in my Z90...) and see what needs to be fiddled. 
I do have extra floppy drives, which I'd be willing to toy with for it.
Power supply wouldn't be a problem.
...
   Another
interesting question is this:  My H-8 has a strange   wire-wrapped
 > breadboard, on top of what appears to be a normal 8080 CPU  
...
  Sounds like a homebrew Z80 modification board. Useful,
but
 I'd probably
 go back to the 8080 if it was my machine.... 
Yep, my guess is that it's definitely a homebrew z80 modification. :)  I
might consider switching to 8080 again, but I do like the z80, and the
home-made daughtercard is amusing, so I probably won't remove it permanently
until I decide how it actually works.
...
   toying around?
(Did CP/M ever run on these?) 
 Isn't there some issue about the H8 having ROM at location 0
 (standard
 CP/M needs RAM there)? I seem to remember there were special  
I believe you're right that the H8 has ROM there.  It may be possible to
change that with jumpers or switches.  My systems has something which could
be an "extended configuration" board, which is mentioned on one of the
previous web-pages as allowing you to run CP/M.  I'm not sure what it does
to allow it, though.
...
  CP/M will run on an 8080 BTW. But a fair number of
'normal'
 CP/M programs
 need a Z80. 
I see -- didn't know that.
Regards,
Chris
Christopher Smith, Perl Developer
Amdocs - Champaign, IL
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