Subject: Re: New finds: enough Torch stuff to sink a battleship

From: Jules Richardson<[email-masked]>
Date: Wed Jul 2 19:38:25 2003

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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---

From: [email-masked] (Tony Duell)
Date: Wed Jul 2 19:38:36 2003

> chips and the like. I got an email from the guy today saying the following:

The VME interface doesn't have any big chips. It's TTL buffers and a few 
small PALs...

> Interesting. I noticed that Simon ROM and wondered what it did :-)

Hmmm.. i have Simon too, but I thought it still needed the key disk. It 
lets you boot from arbitrary files on the hard disk, though which is what 
makes it useful. But UniPlus+ still seems to need a key disk to boot...

> that's what the 10" ones are like inside. I pulled the case the other day to

I am not sure if mine is the 10" or 13"... 

Looking from the back there's the video PCB flat in the bottom. On the 
left is the PSU PCB with the chopper control PCB plugged into it. On the 
right is the scan PCB with the raster correction PCB plugged into it. 
There are a couple of other PCBs for the controls, and the Hstat block 
screwed to the metalwork...

> that's something to do with the power-mechanism bypass (or might well be

Can't help you. The power control is handled via the service processor 
(6803 IIRC)...

> No, not on the SASI board. There's a Torch ROM on the Xebec controller, but the

It's not going to try to boot from that...

-tony