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 A "Primitive Computer" built by two students in 1978 
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Joined: Tue Dec 18, 2018 11:25 am
Posts: 41
Location: Hampshire, UK.

This computer came into existance as the result of a set of course notes at the University of New Brunswick (Fredricton N.B. Canada) written by L. Johnston describing a "Primitive Computer". In 1977, G. Morrison and S. Kyle, two students graduating in the class of 78 decided to construct the machine as their final project. Nearly a year in construction, the machine worked, and was successfully demonstrated running a small program.

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It is a wire wrapped machine built from TTL chips. It has 16 bit data path and uses four 74281s for the ALU and around 36 other TTL chips (excluding the external memory boards). Single address machine with one accumulator, a 12 bit address allowing for up to 4096 words of memory, and up to 16 instructions but only 7 were implemented due to lack of time:- LDA, STA, ADD, SUB, JMP, BNE, HLT. The remaining instructions are all NOP. No I/O and programs are entered via the front panel address and data switches only.
Block diagram here...
And their final report (2.8Mb) here ...

Wed May 13, 2020 7:10 pm

Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1666
Very nice! I hadn't come across the 281 - it's got a shifter. Datasheet in this book ... /Am25LS281

There's a table of ALU parts here ... rev=search

Thu May 14, 2020 6:03 am
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