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Some Minimal Instruction Set CPUs
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oldben
Joined: Mon Oct 07, 2019 2:41 am Posts: 215
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Nov 1977 Byte Mag, has " Build a computer from scratch". It is a 8 bitter, 4 instructions In,Add,Store(negitive),Jump if Postitive. Ben.
Last edited by BigEd on Fri Nov 13, 2020 10:45 am, edited 1 time in total.
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Fri Nov 13, 2020 10:29 am |
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B.Bibby
Joined: Tue Dec 18, 2018 11:25 am Posts: 37 Location: Hampshire, UK.
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https://archive.org/details/byte-magazine-1977-11/page/n78/mode/1upIt is a very minimal instruction set, but neatly tackles the bootstrap problem with its WIO instruction. Code: ”WIO 00xxxxxx Wait for input to location N. Display current contents of location N while waiting.” Although entering a program by this method would be a little tedious, it seems good enough for entering a small secondary bootstrap. It is very similar to the method used in the CARDIAC paper computer. https://www.cs.drexel.edu/~bls96/museum/cardiac.html
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Fri Nov 13, 2020 11:02 am |
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BigEd
Joined: Wed Jan 09, 2013 6:54 pm Posts: 1579
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I've a feeling the 1802 similarly supports a front panel bootstrap
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Fri Nov 13, 2020 12:04 pm |
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monsonite
Joined: Mon Aug 14, 2017 8:23 am Posts: 153
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Nice to see a bit of home-built TTL computing history.
However it had a chip-count of 35 ICs, of which 8 were the RAM.
The instruction set was very minimal - leaving a lot of scope for future improvements.
I would have thought that using a pair of 7418s as the ALU would have encouraged a more diverse instruction set.
In the author's defense - it was his first electronic project, and he learnt a lot about TTL design from the exercise - and he got an article published in BYTE !
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Fri Nov 13, 2020 12:32 pm |
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