Date   : Wed, 12 Feb 2014 09:52:16 +1100
From   : mark@... (Mark Ashley)
Subject: Paged ROM board

There's a review of a Sir board on page 21 of this... it's hard to tell if
it's the same board from the picture. I suspect "rom 2" in your picture
denotes version 2 of their board. Pretty ordinary review anyway.

ftp://ftp.stardot.org.uk/pub/docs/magazines/beebug/volume02/greyscale/BeebUG%20Volume%2002%20Number%2006%20November%201983.pdf

Some people mention they got theirs working, after asking the same
questions about documentation...

http://lists.cloud9.co.uk/pipermail/bbc-micro/2007-February/000707.html

Might be worth chasing him up. rhobbis@...
<bbc-micro%40lists.cloud9.co.uk?Subject=%5BBBC-Micro%5D%20Sir%20Computers%2012%20ROM%20Board%20-%20installation%3F&In-Reply-To=>though
because of the other pictures there I think he's sold his Beeb stuff.




On Wed, Feb 12, 2014@... AM, Peter Coghlan <bbcmicro@...>wrote:

>
> My original Model B has developed a fault in the ROMSEL latch, IC76
> (74LS163).
> It can't find any paged ROMs and reports "Language?" every time at startup.
>
> On looking it up, I found that a 74LS163 is really a loadable counter but
> Acorn
> suppressed the counting part of it, using it as just a 4 bit latch.  Mine
> has
> decided that it now wants to live out it's designers original intention as
> a
> counter and is going to count, no matter what Acorn intended :-(
>
> (I hope I didn't cause this by loading down one of it's unused outputs by
> connecting it to A14 on three 32K EPROMS to give me six ROM images without
> requiring any extra hardware.)
>
> Rather than experience the pain of sourcing a replacement 74LS163, I went
> to
> have a look at what was in the box of Beeb related spares and found this:
>
> http://www.beyondthepale.ie/board.jpg
>
> I can't recall where I got it, probably in a box of miscellaneous stuff in
> an electronics shop.
>
> The only identification on the board is "SIR COMPUTERS Ltd 1983" except
> for the
> giveaway legend "BBC ROM" beside the two pin header where a flying lead is
> plugged in and a tiny etched "rom 2" at the bottom left.  Given that there
> are
> also twelve 28 pin IC sockets labelled IC0 to IC11, it appears this is a
> sideways ROM board for the Beeb.  When I google this, I get is lots of
> matches
> for Sir Clive Sinclair :-( and a few references to a company in Cardiff
> making
> Acorn related equipment.
>
> SKT1 and IC23 appear to be wired in parallel and match the pinout of a
> 6502.
> The sticker placed over the IC23 pads suggest that they are not intended to
> be used (unless maybe the shop put it there) and a short ribbon cable
> adaptor
> of some kind must be used to connect SKT1, the 6502 and the 6502 socket on
> the
> Beeb mainboard.  The three fixing holes don't seem to line up with
> anything in
> a model B so it would appear the board can only be stuck inside the lid.
>
> On the plus side, it has a 74LS373 latch so it would appear to be able to
> work without a functioning ROMSEL in the Beeb.  It seems that the flying
> lead
> might plug into S21sw to enable the four ROM sockets in the Beeb (which
> would
> then be usable if there was a functioning ROMSEL to select them).
>
> Does anyone know anything about this board?  In particular, can anyone save
> me having to figure out what the jumpers labelled A to L are for?
>
> Regards,
> Peter Coghlan.
>
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