15 Apr
2010
15 Apr
'10
11:45 a.m.
On Wed, Apr 14, 2010 at 1:01 PM, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I think it would be easier/better to make the daughterboard. I can think
of several reasons for this :
It's what HP originally designed (and I prefer to keep machines as
original as possible unless there are very good reasons not to do so)
The ROM module connector carries signals for 4 banks of 128K*16 bit ROMs
(IIRC). That is 17 address lines, 16 data lines and 4 chip selects. The
OS ROM PCB (at least the System V one) carreis 4 ROMs, each 128*8 bits,
using 2 of the chip selects and the optional daughter board carries the
other 4 ROms using the other 2 chip selects. Yes it would be trivial to
re-encode the chip-selects back to 2 mroe address lines, but why bother?
I don;t know what the largest easyily-obtainable EPROM is now.
The OS ROM PCB connects to the rest of the machine by having 2 rows of
plated-through holes which are then gold plated and which fit over pins on
the Logic A PCB. Making this would be impossible at home, and it may be
non-trivial to get it done commercially and have it relable after any
insertions/removeals. The option board connects to the OS ROM PCB by a
pair of header connectors that would be easy to obtain and solder to the PCB.
You would have to copy the OS into the new ROMs if you made an all-in-one
PCB. I don't know about copyright issues here. And you'd have to copy the
OS into every ROM set you wanted to use (rather than having several
daughterboasrds which you could just fit into the OS module if you wanted
to change the option ROMs.
The option PCB was just ROMs, nothing else. I see no reason not to keep
it like that.
2) The later version of the OS ROM module has a space for an option ROM
PCB. It seems like this would be trivial to recreate (schematics of the
ROM Mmodule, inclding the pinouts of the option board connectors are
certainly in 'my' Integral schematics). If enough people are interesd,
it might be worth laying out a PCB...
I had an OS ROM module with BASIC in ROM on the daughter card. I no
longer have an Integral. Would it be any easier or more difficult to
create a whole new ROM module board vs. creating a daughter card to
fit an existing ROM module board? I suppose you might not have space
to fit all of the ROMs on a single board if you wanted to use through
hole components. When I still had my Integral I was thinking it would
be interesting if
someone could create a new ROM board for the expansion slots that
could be loaded with the contents of the Software Development ROM
module.
The scheamtics of the HP EPROM PCB are available. IIRC, it's just simple
logic (address decoders, buffers) and could easilty be reproducted. The
other one worht reproducing would be the serial PCB which is again very
simple.
-tony