FPGA VAX update

Sridhar Ayengar ploopster at gmail.com
Wed Nov 2 13:16:58 CST 2005

der Mouse wrote:
>>>I guess nobody even considers building a computer from scratch. :(
>>Wasn't there an article a looong time ago about a fellow who built
>>his own CPU from TTL parts in BYTE or Microcomputing?
> I dunno about that, but I once did just that.  I took a digital
> hardware design course, and as a term project I breadboarded a little
> 4-bit computer.  (I think the whole class did likewise, but it was long
> enough ago that memory is fuzzy.)  Only 16 words of memory, and 4-bit
> words at that, with 4-bit opcodes - not a terribly powerful machine,
> but an extremely instructive one to build.  All TTL; the most
> complicated building block was a 4-bit ALU chip, a 74181 I think.

We had to do something similar in our hardware design course.  We had a 
choice.  We could actually etch boards and solder sockets, breadboard it 
or simulate it.  We had sixteen banks of sixteen locations, four bits 
each.  And we didn't have branch instructions.  Only relative jumps.

Most (all but 5?) students simulated it.  I breadboarded.  (I hadn't yet 
learned soldering then.)  One guy soldered it.  Probably made a pretty 
good souvenir.

Peace...  Sridhar

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