On 5/11/2010 7:41 AM, Invisible wrote:

>
> You know that there are people who do scientific experiments *about*
> computer programs, right? ;-)
>

Yeah :)

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. I have 
the ALU designed. (Fairly simple, it can add, perform bitwise logic and 
shift, as well as calculate the twos complement. Other operations will 
take multiple cycles) I also have most of the control logic put 
together, but I need to make some changes to ensure an ALU instruction 
can occur within 2 cycles (One to latch the ALU result, one to store the 
result in the accumulator)

Eventually, I want to take a simplified version of that design and 
create a CPU entirely out of relays. Obviously, I'd need keep the design 
as simple as possible, but still functional to keep the relay count 
down. Something about a bit stack of clacking relays with blinking 
lights really appeals to me. That machine will likely still have IC 
memory, though, but the registers will be relay latches.

One consideration for the relay version is that the machine should be 
able to halt and only resume processing on an interrupt. So, ideally, 
you'd give it inputs, issue a command, and send it clacking away to get 
a result.

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...

The TTL version should be fun, too. I plan to have lots of LEDs to show 
what's happening inside the machine.


-- 
~Mike

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