Date   : Wed, 04 Jul 2007 23:18:51 +0100
From   : mike@... (Mike Tomlinson)
Subject: Anyone recognise this board?

In article <36704.82.71.113.222.1183549419.squirrel@...
net.co.uk>, Richard Gellman <splodge@...> writes

>I'd be hazzarding a guess here, but it looks like a ROM board with a
>curiously complex address decode logic.

I agree.

>I would suggest the "two closely spaced IDCs" were actually an IC header,
>and the ribbon plugged into a ROM socket.

I thought it might be for two 34-way IDC headers which would fit in the
ashtray for a ROM cartridge system.

>The large chip at the top right appears to be a ROM of some sort,

It's PB05 - the Acorn BASIC II ROM.

> the rest
>is all 74-series logic. The 74244s and 74245s are bus buffers, which is
>curious for anything plugging into a ROM socket,

possibly to deal with the cable length to the headers.

> and the presence of the
>74138 3-to-8 decoder and the 74163 flip-flop are puzzling too.

ROM select line decoding?

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