13 Dec
2004
13 Dec
'04
11:42 a.m.
Tony wrote:
I believe mine is a 9845B. I've not got the case parts where I can easily
see them (the PCBs being more interesting are what cover my bench :-)),
but some of tha add-on ROM modules say '9845B' on them. I have a
monochrome monitor.
Incidentally, one of the ROM modules is a 3rd party one. Rather than
being an HP ceramic hybrid in a plasic holder, this is a little PCB with
2 2764 EPROMs on one side, a couple of '373s and a small PROM (address
decoder, I guess) on the other. This will be useful in figuring out
pinouts, etc.
My workbench is currently covered with a 9845 is
many bits :-). And I am
slowly figuring out just what's inside that darn machine...
I don't know about the service toolkit.
There were apparently major software changes between the 9845A and 9845B.
However, for the 9845B and 9845C there are two different processor
options. The original uses two HP "BPC" microprocessors, as described
in HP Journal articles. This is the same 16-bit microprocessor used
in the 9825 and 9835, and in various peripherals including the 9872
I haev one of those. I don't think it's the same device -- exactly -- as
in a 9825, it appears to have more connections for a start. It is almost
certainly the same architecture, though.
plotters. Later there was a higher-performance CPU
option using
commercial bit-slice parts. Probably 2901s, but I've never seen one
I have that. It's 3 PCBs with a little backplane on top to link them
together. One of the PCBs goes into the main backplane, and seems to
contain mostly TTL, with 8 of what appear to be RAMs (but I can't
identify them exaclty yet. All have the same 1816-xxxx number, all are
made by AMD). The middle board ofthe 'sandwich' contains 4 2901 ALUs (you
are right) + more TTL. The last board has a 2910 sequencer, some ROMs
(microcode store, I guess), more TTL, including a 74150 which I assume is
the con=dition bit multiplexer.
so I can't say with any certainty. I'd expect
that the I/O processor
would still be a BPC.
It is, or at least it is in my machine. I've traced the I/O bus
connections to that board anyway -- the one thing I know for sure is the
pinout of the I/O slot. Incidentally, the I/O backplane contains a lot of
buffer chips, a bit like a cut down 9878.
-tony