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 Some Minimal Instruction Set CPUs 
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Joined: Mon Oct 07, 2019 2:41 am
Posts: 215
Nov 1977 Byte Mag, has "Build a computer from scratch".
It is a 8 bitter, 4 instructions In,Add,Store(negitive),Jump if Postitive.

Last edited by BigEd on Fri Nov 13, 2020 10:45 am, edited 1 time in total.


Fri Nov 13, 2020 10:29 am

Joined: Tue Dec 18, 2018 11:25 am
Posts: 37
Location: Hampshire, UK.

It is a very minimal instruction set, but neatly tackles the bootstrap problem with its WIO instruction.
”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.

Fri Nov 13, 2020 11:02 am

Joined: Wed Jan 09, 2013 6:54 pm
Posts: 1579
I've a feeling the 1802 similarly supports a front panel bootstrap

Fri Nov 13, 2020 12:04 pm

Joined: Mon Aug 14, 2017 8:23 am
Posts: 153
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 !

Fri Nov 13, 2020 12:32 pm
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