1 Jul
2003
1 Jul
'03
10:06 a.m.
Hi Tony,
No idea... What (if any) chips are missing from your
Stickleback, other
than the Ethernet chipset?
I haven't had time to open the case today, but a glance the other day didn't
show anything big around the VME bus interface; it looked to all be 16 pin
chips and the like. I got an email from the guy today saying the following:
[ Not a theory - I know that one is the original prototype. The VME interface
[ didn't work on that PCB issue. I've an idea that it's got a prototype EPROM
[ in it that doesn't require a key disk. IIRC on that box of Eproms I gave you
[ there is a "Simon" eprom - that's a debug boot EPROM that doesn't use
the
[ key disk system
Interesting. I noticed that Simon ROM and wondered what it did :-)
I thought that at least one of the monitors actually
started by combining
the syncs to make composite sync (and thus you could feed composite sync
in on one of the pins). I will have to dig out the schematics...
that could well be true - what I thought was a sync splitter board in that 725
turned out to just be some buffer circuitry; the output was still composite.
How someone managed to blow the fuses for the RGB and sync lines I don't
know...
The monitor I am thinking of is almost entirely a Sony
chassis, with a
little Torch PCB at the input carrying the 8 pin DIN socket and
connectors to the monitor video board (flat in the bottom) and the speaker.
that's what the 10" ones are like inside. I pulled the case the other day to
see what the connections were but didn't need to go any further than the small
PCB carrying the connector so I don't know what's lurking deeper within (yet)
I think that 'NC' pin is for the interrupt
input from the touch switch.
there's some bodged circuitry (cut tracks, extra capacitor and a desoldered
resistor etc.) in the corner of the board near the video circuitry. Maybe
that's something to do with the power-mechanism bypass (or might well be
something else entirely)
Watch out -- if the NICd goes open-circuit, then the
clock
chip might end up getting 12V....
nice! :-)
[SASI controller]
One question? Is there a ROM or EPROM on this board
connected to the 1MHz
bus side of things? The reason I ask is that there's some feature of the
BBC micro where you can get it to execute code from a ROM in one of the
1MHz bus address spaces after a reset, if you hold one of the interrupt
lines low or something. I wonder if that's where it gets the hard disk
drivers from...
No, not on the SASI board. There's a Torch ROM on the Xebec controller, but the
machine was locking up with the Xebec board disconnected and just the SASI
board in place. Unless the presence of the SASI board is enough for the machine
to think the Xebec board's there too whether it is or not. No idea what would
happen then...
The Torch _SCSI_ interface just has a normal sideways
EPROM (SCSIFS) in
one of the Beeb mainboard sockets, BTW...
Hmm. I need to open up cases again. I remember the 725 box having a "Unix host"
ROM, standard Basic / OS / DFS, and the ECO Econet ROM. Will go digging
tomorrow...
cheers
Jules
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