15 Feb
2007
15 Feb
'07
11:45 p.m.
Tony Duell wrote:
There are 2 versions of the HP9815 processor board.
The original one uses
2112 RAMs (256*4), and 2Kbyte ROM chips. It's laid out for 8 such chips,
only 7 are fitted (so 14K of ROM). This board can take a RAM expansion
board that mounts on the track side (top) of the PCB at the rear edge.
I opened it up and the 7 ROM chips are pretty obvious, I must have
seen them before. The 6800 is marked only with HP's house number, so I'm
guessing I read something somewhere that told me it was a 6800 and left me
with the impression there was only 2K of ROM.
14K of firmware code certainly makes more sense.
I've had my 9815 totally apart, of course. If
you're tempted to do the
same, can I recmend against dismantling the keyboard. For one thing the
PCB is held down by around 100 timy screws. And when you get the PCB off,
the keycpas fall out and are a right pain to get back. Don't ask....
On the unit I have ~ 9 of every 10 of those tiny screws is instead a push-pin
inserted into the plastic, so the keyboard isn't about to come apart without a
high likelihood of breaking things. I'd rather have the screws, for cleaning
and potential repairs.
Suffice it to day I had to send a panic e-mail to a
couple of lists
asking for the order of keycaps in part of the keyboard...
(.. or power it up, press the keys and find out what they do..)