22 Jul
2012
22 Jul
'12
5:21 p.m.
On Jul 22, 2012, at 2:47 PM, Tony Duell wrote:
This one seems to have a third party backplane that will accept six boards on the right
side. There is also a module plugged into one of the slots on the left side that looks
like extended memory.
TMS9918
I don't see any way to discover what they're connected to without doing a major
disassembly.
I've tried to disassemble as little as possible so far. The disk controllers I believe
are standard Heathkit ones. I've looked up the board numbers and they seem to
correspond to the hard-sectored controller and the double density soft-sectored
controller. The double density board has a floppy controller chip on it.
Hi Dwight,
Thanks for your suggestions.
I just opened up my H89 and there are a bunch of modules plugged into
a backplane. The backplane itself is labeled "mako data products MH89
plus 3". I guess it's a third party module. Plugged into it were the
following modules:
That does not sound like a 'stock' H89. The original layout was somethign
like :
At hte back are 2 large-ish PCBs. The rearmost one is the H19/Z19
terminal (Z80 baseed). In front of it is another Z80 processor board that
runs the user software (CPM, etc). There are 6 (IIRC) connectors o nthis
board for add-ones, 3 each side of the CRT neck. They are not all the
same by any means. One of the ones on the left is normally ued for an
eaxta 16K RAM card (which is bank-switched with the boot ROM, etc). The
ones on the right normally hold a triple RS222 port card and 1 or 2
floppy controllers.
DISK I/O 85-2601-1
DOUBLE DENSITY 85-2597-1
SERIAL/PARALLEL I/O BOARD
N.O.G.D.S HA-89-3-B
ATRA H-101-A with a H-201-B daughterboard
The last two seem like they have something to do with sound generation
and the N.O.G.D.S. board also has a video chip on it.
WHich video chip?
Wheee is the processor in all this? Do you have the H89 docuemntation? If
so, is there any similarly between your machine and the docs?
Sorry, I failed to mention that the normal CPU and terminal boards are behind the CRT at
the back of the case.
Beyond that, there are six toggle switches mounted between the main
keyboard and the numeric keypad and another toggle switch mounted on the
floppy drive along with a second LED.
Cerainly non-standerd. Whare are the switches and LED connected to?
Do you have any idea what any of this stuff is? In particular, do you
know if the two disk controller boards are for hard or soft sectored
drives?
The drive are the same, there's no index/sector pulse seapration don in
5.25" drives.
IRIC, the oriignal Heathkit controlelr was for hard sectored disks, and
used a synchronous serial chip and soem glue logic. Nothing that screams
'floppy controller'. The double-desnity card ad a Western Digital
(WD179x?) chip on it, and used soft-sectoroed disks.
I'd look at the cards you have, see if you vna identify any of the ICs. -tony