14 Sep
2010
14 Sep
'10
1:03 p.m.
That's right. The Extended I/O ROM is built in.
Under the cover, the following
are listed:
9872A plotter, Genereal I/O, Extended I/O, Adv. Programming, String, Sytem
Programming
I can never rememebr all the suffix letters for the 9825 series :-). But
from what I remember, the earlier/simpler machines ahve
the HPL firmware
in a modle that slots into the RHS of the machine. The memroy
boards in
the 'stack' are just RAM, either 4K or 8K words. All extension ROms have
to be added by front port modules.
Later machines have a ROM/RAM board on top of the 'stack' It contains the
HPL firmware and most of the extnsrtion ROMs. IIRC there's a DIP switch
to select between the 9862 and 9872 plotter ROMs. The RHS module is not
used, there's a cover clipped over the hole, and a couple of track cuts
on the processor board to disable it (these cuts my be hiddeb my the CPU
hybrid.
The top model (IMHO) has thatr with another special 16K word RAM board under
the ROM/RAM board. With that one you get soemthing like 31K words of RAM
_and_ almost all the ROMs.
From the hp9825.com site, I gather that it should
be possible to transfer
programs to and from the 9825 in ASCII format via the
serial card and
some Sytem
Programming ROM routine. Not exactly the same as mass storage, but
better than nothing. > It's also advisable to add a crowbar
circuit to the psu the 723 regulator
> IC's and power transistors don't life forever. When they go you will be
> grateful for adding the crowbar circuitry.
Seconded!
I plan to do this. Any pointers from those who have done the mod?