4 Bit Homemade Computer

[Ashbad]

Me and my friend spent last weekend making a 2 bit computer out of ONLY household items.

What we used:

-6 nails
-3 miniature cardboard boxes
-6 low charge magnets
-tons of wire



anyways, no picture yet, my friend is gonna give me a few pictures on monday -- hopefully by then we can allow for writing of programs in nibble hex using switches

Here's the plan on what the possible opcode table will be:

0 - NOP
1 - ADD O, A, B
2 - SUB O, A, B
3 - ADD A, B
4 - SUB A, B
5 - OUT A
6 - OUT B
7 - IN A
8 - IN B
9 - AND A, B
A - LD A, PC$ + 1
B - LD B, PC$ + 1
C - OUT PC$ + 1
D - AND A, B
E - IN PC$
F - RET

To do this program writing however, we'll need more materials -- we'll try to find the cheapest switches available and more copper wire, we already use a full roll

[aeTIos]

Sounds freakin' awesome!
and haha, your avatar reminds me of one of my teachers O.x

[Binder News]

Ohhh. Sounds like fun! I just spent half my math class diagnosing the problems with 4 of the schools "broken" calcs. 1 had battery acid. 3 had messed up LCDs, and one of those was still usable w/o getting the LCD replaced.

EDIT: And I still got 3 problems on my homework done!

[Ashbad]

lol O.X

yeah it's pretty awesome.  I actually think it's possible that the calculations are considered really fast compared to other microprocessors -- you hook up the right wires, and then turn on the power wire, then BOOM! you hear a click of the bits setting to the result in the O register.

Right now we only have addition and subtraction "machines", but and AND one will be even easier the harder one was the SUB one took an hour of figuring out a diagram.  Though, with 2 bit, it's possible that we can use the ADD operator for AND operations -- but then ADD will have no overload looping.  We still are figuring out how to do that.

I think Xeda will like the opcode table

[Freyaday]

This isn't a microprocessor. It's a macroprocessor.

[Ashbad]

O.o good point

Anyways, I found the schematic for an earlier design of this, which formed the basis for the AND machine (my friend called and said it's now working)

this was going to be an ADD machine, but now since we're gonna try to deal with overflow, we'll use it instead for AND operations

And, we're discussing to see if going from 4 bit instructions (hex) to 5 bit instructions (base 32) will make this more awesome and allow for things such as conditionals and such.  those will be hard to make though

Well, schematic:

EDIT: and yes it's much more complex now this was like the very first edition

[Freyaday]

So this is a circuitous diagram?

[Ashbad]

somewhat I suck at making those, so many symbols, so I kinda just represented things with pictures and such. 

Also, apparently, jumping around the program WILL be possible -- but I have no idea about conditionals -- I know how to wire up to the logic machines themselves, but how I'll make them DO the operations will be harder

[Freyaday]

What's the power source?

[Ashbad]

at the moment, simple AAA's

Also, I think I'll think about thinking about using both 4 bit registers (not THAT much more work thinking wise) and 8 bit RISC instructions, with a prefix and suffix nibble

[Freyaday]

Wait-that's three nibbles!

[AngelFish]

If he's using a 4 bit word size, that's not a problem

EDIT: Topic name change 

[Ashbad]

3 nibbles would be nice, but there's only one prefix and one suffix nibble == 2 nibbles

maybe I should've said "Prefix and fields nibble" my bad

[Freyaday]

That seems to be the case, given the new title of this topic.

[Ashbad]

yep

I realized that since it wouldn't be horribly hard to up the bit number (past a certain extent), I might as well

I wonder if I should also make an assembler that changes stuff from mnemonics to a diagram of bits... though for right now, construction and such.