[geeks] Crackpot project, need some guidance

[Mouse]

> I just thought I'd let you guys know how my ongoing project was
> progressing.

Thank you.  I, for one, am interested.

> My task after I've proven my ALU is to lash up a simple 16-bit CPU
> and build a rudimentary machine code for it and see if I can add a
> couple of numbers together then subtract them to get back to the same
> result.  You'll probably hear the cheers from over there if it
> actually works :D

One of the things I did in university was to build a small 4-bit CPU
from discrete logic; the most complex package we used was a 4-bit ALU
chip (4 bits input A, 4 bits input B, 1 bit in for things like carry
in, 4 bits output plus a fifth bit for things like carry out, and
three? four? bits that specified what operation to perform).  It was
great fun.

If you want to do a 16-bit CPU in discrete logic you may find it
easiest to do it serially, one bit at a time.  It will divide your
effective clock rate by 16, but for what you're doing that may not be a
problem, and it will greatly reduce the amount of hardware needed at
many points.

> This has been the single most enlightening project I've done in a
> very long time.

I agree: playing with hardware is tremedously fun and incredibly
educational.  I like to understand everything I work with at as many
levels as I can; it's (almost) always fun and occasionally even useful!

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