>>> It's tempting to get something like an FPGA test board and poke
>>> something into it, though.... but I feel this will take some of the "I
>>> built it myself" satisfaction from the project.
>>
>>  From time to time, people try to build ray tracers using FPGA. And,
>> occasionally, they make one that out-performs a software ray tracer
>> running on a quad-core Xeon or something. So don't go thinking that just
>> because it's FPGA it can't be fast; special-purpose machines can and
>> sometimes do out-perform general-purpose machines. ;-)
> 
> I didn't say anything about the speed. Some of them clock at hundreds of 
> MHz... which is why they would excel in applications such as a 
> customized DSP.

I was thinking more along the lines of watching a ray-tracer running in 
near-realtime, and knowing you couldn't possibly be doing that unless 
you'd built the hardware yourself. But yeah, I guess it's not the same. 
(It's also presumably not very easy...!)

>> You know that the first computers filled entire buildings, right? ;-)
> 
> Right. Which is why it must be as simple as possible, because I don't 
> need to dedicate a 20'x24' room to the thing ;)

With the reinforced flooring, and the custom air conditioning system, 
and the specialist PSU, and the team of technitions to tend to the 
beast's needs? ;-)

> Thankfully memory is 
> nice and solid-state, nowadays!, no need for ferrite cores, drums, relay 
> latches or any of that nonesense.

It strikes me that if you had a relay without a spring, you could use a 
single relay as a kind of mechanical memory.

It also strikes me that you could really easily "cheat" and hide a small 
Z80 under one of the relays and fake the whole exercise! :-D

> Of course, the relay-based machine may be simplified to the point where 
> it can't do anything but play tic-tac-toe...

No, you only need some marbles in matchboxes for that. ;-)

> more than space, my biggest concern is power usage. I need to be able to 
> operate off of a 15-amp breaker without tripping the thing. (That's 15a 
> @120v, btw... not 240v!

Hmm. Most of your current is going to come from the relays held open. 
The closed ones won't use any power. I have no idea how much power a 
relay uses, but I shouldn't have thought it's that much... Then again, 
just how many are you expecting to have? ;-)

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