New find, Heathkit H89 computer.
ard at p850ug1.demon.co.uk
Mon Sep 25 16:28:14 CDT 2006
> There were soft sectored cards but these were uncommon. The
But they do exist, there's one in my Z90.
It's possible to have 2 disk controllers installed at the same time (with
some restrictions). My Z90 has the hard sectored controller linked to the
intenral drive, and a soft-sectored controller linked to a pair of
> hard sectored drives used a USRT on the controller card. The soft
> sectored used a regular disk controller. The ones in the H8's used
Mine uses a WD1793 and the normal support circuitry.
> a Z80 but I don't think this was the way it was done on the H89.
No, there are only 2 Z80s in the case. One to run user programs, one as
part od the 'H19 terminal'
> As for CP/M, the machine needed a special logic array chip to do
Wasn't this standard on the H89, etc?
The chip is one of those fusible link PROMs I think. A couple of output
ports are used to set whether the memory map is set up for HDOS or
CP/M. I have dumps of the memory mapping PROMs (and for that matter the
other PROMs in the machine) to hand, but you need the schematics if you
intend modifying things. These ROM iamges came from my machine which
certainly can run CP/M.
More information about the cctech