|
![](/i/fill.gif) |
>> You know that there are people who do scientific experiments *about*
>> computer programs, right? ;-)
>
> Yeah :)
OK, good. :-)
> Actually, in the vein of computer science: For the fun of it I'm
> designing CPU from scratch. I plan to build it with TTL gates after I
> have the design complete and have vetted it through simulation.
...this sounds so much like my life approximately 15 years ago...
> Eventually, I want to take a simplified version of that design and
> create a CPU entirely out of relays.
> Something about a bit stack of clacking relays with blinking
> lights really appeals to me.
Hmm, interesting.
Perhaps you would have enjoyed a visit to Stoney Stratford telephone
exchange. It's a sprawling building, filled with rack after rack after
rack of cases, each case filled with dozens of relays. And they're not
in cases or anything, just "naked", so you can see (and if you desire,
move) the working components. There is also several tonnes of wire
overhead feeding this equipment. And all of it is as silent as death.
It's like a museum or something.
(Just down the corridor there's a small broom cupboard. This is the
*real* telephone exchange, alive and operational. It's really just a few
lasers and some circuit boards. But mess with it and you'll have just
taken 15,000 customers offline!)
Myself, I visualised a computer made of pressurised water fed through a
series of simple mechanical valves. Sadly, I fear that for reliable
operation, you would need inside water pressure. And if you wanted a
clock speed of more than about 0.02 Hz, you would have to use steel
piping and pyrotechnics to sustain the necessary pressure! It would be a
very "kinetic" experience though.
> It's fun stuff, and occupies a good deal of time. Also a great way to
> learn HOW a computer like the one you're sitting at actually works. e.g.
> how each instruction of machine code does what it does, etc...
Yeah. I've written about it before now. (As I say, a computer is a layer
cake though. Try to explain it and laymen quickly get lost in the layers
of abstraction upon abstraction needed to perform even the most trivial
task.)
Also... when I tried to build my own machine out of 7400s, I quickly
discovered that the gates don't appear to function as their truth table
indicates that they should. (!) I also looked into playing with FPGAs,
but the cost is prohibitive. (And, knowing me, I'd just make something
that doesn't even work, and then spend months trying to find out why!)
Plus, Xilinix (?) have a free simulation tool available, and it's just
painful to use. I dred to think what actually synthesizing with it would
be like...
> The TTL version should be fun, too. I plan to have lots of LEDs to show
> what's happening inside the machine.
In solomn truth, it's probably simpler and easier to code a small peice
of JavaScript that controls a little Flash animation on a computer
screen. But there's something impressive about being able to pick up a
physical object in your hands and see that there really are no tricks...
Post a reply to this message
|
![](/i/fill.gif) |