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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment. |
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8th Aug 2020, 7:52 pm | #1 |
Hexode
Join Date: Oct 2007
Location: Ossett, West Yorkshire, UK.
Posts: 399
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Unknown ROM RAM board
Hi folks,
Does anyone recognise this board? I thought it ought be a ROM ram expansion for a BBC Micro but the only identification on it is "2nd GENERATION". I've googled it and looked at a number of 8 bit websites but can't find anything related to it. It has 5 wires attached labelled 0 1 C B and A. The 2 ICS are 74ls138 and 74ls32. David |
9th Aug 2020, 6:17 am | #2 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,188
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Re: Unknown Rom Ram board
It certainly looks like a sideways ROM expansion board for a Beeb.
The 5 extra wires may be to connect to the sideways ROM select register on the BBC mainboard (to enable the extra ROMs), maybe R/W if the board supports RAM. It looks like it would tke about 10 minutes to trace out that extra logic (3 line to 8 line decoder pretty much has to be to select the ROMs, the quad 2-input OR gate could be for a number of things) which would I think be the next step. |