;DI just happen to be doing exactly this, with a twist: It's my own CPU, with its own handbuilt gates. It also runs in base 4.

I designed and built all the gates, and an adder, last year. I built an AND, OR, and NOT gate. ANDs comprise an OR and three NOTs, two on in, one on out. It works.


It really works, even in binary it also follows all proofs applied to Binary logic. XORs can't exist, really, unless someone can come up with a way.

base 4 computing is the way of the future. This design will be expandable to any base you want, but higher bases mean higher voltages, and base 4 is already reaching fairly unsafe (~36 V in the adder) levels anyways.

I made the first gates for a State Science fair project, got second place. This year I'm making a programmable CPU. 

You may be wondering-why base 4?

I just wish it was easier. This design stuff is hard! My first design used lots of opamps, but my OR gate now only needs 2 components.

Well, this is definitely giving us experience in designing the thing. We can make our own processors!

Oh actually OTCalc used a pre-made one.

This is really awesome!  I've been playing around with it a little for about an hour, and I've been making my own processor.  I have a nice set up for registers, I think, but I'm not sure how I should start interpreting opcodes.  Thoughts?

EDIT: I think I have figured out a way, and uploaded the new circuit with a demonstration.

Now that I turned in my project and had it graded, I think I can upload it online.  Here is the CPU I made.  I spent a lot of time organizing it into subcircuits which is a really helpful technique.  It's a 16-bit RISC processor with 4 registers and there's about 20 different instructions.

I also have a conway's game of life program that can be loaded into the rom.  Its really slow since it has to go pixel by pixel so it takes about a minute for each generation at the fastest clock speed.  The first 12 words of ram are the screen buffer.  A good starting configuration to test is the first 4 bytes: 0x0000, 0x0040, 0x0050, 0x0060 which makes a glider.  Feel free to use elements of this in your designs if you're having trouble with any part.

Oh, Cool! I didn't know I could do that with the different parts of the circuit! Here I've been working with an increasingly cluttered mess! Well, I have no experience wit this kind of a thing, so I am still trying to figure things out with using the clock for the interpreter. I have it so that the interpreter recognises loads between registers, I just need to use a clock to time things just right... Well, I could just redesign some of the circuit and that would make it run faster, but it would use more components

this is really very cool! I have worked with a program that looks like it, but didn't do anything usefull, and was full of bugs. really stupid bugs. I like hardware, but prefer software. I will use this program one day, that's for sure!

Alright so i have been exremely busy working on my CPU, and it is almost finished.  It currently has about 40 different oppcodes, with many different arguments.  The features it currently supports are these:

Hardware:
4 Registers
256 bytes of program ROM
256 bytes of memory RAM
8 byte address stack
Memory mapped LCD
text output
text input
numerical input
Zero and carry flags for conditions

Commands:
Loading Registers into registers
Loading constants into registers
Loading constants into RAM
Loading Ram into registers
Loading ROM into registers
Loading random numbers into register
Loading random numbers into RAM
Jumping to other parts in the program
Jumping conditionally to other parts in the program
Calling other parts of the program
Calling conditionally other parts in the program
Returning from calls
Doing arithmetic on a register and A (Adding/Subtract/Multiply/Divide/Mod/XOR/AND/OR)
Doing arithmetic on a constant and a register
Doing arithmetic on a register (increment/decrement/Clear/Negae/Shift Right/Left with carry/Shift right/left circularly)
Decrement B and Jump to address if not zero (for loops)
refresh the LCD
Output a character stored in a register
Clear the text screen
Terminate the program
Terminate on a condition

i have come up with the definition of logisim.

Logisim: when a computer emulates a computer which runs a program that allows a user to create a computer and then emulate it.

breakdown:
first, you start with your hardware computer, which is emulating the JVM (java virtual machine, what java runs on), which is running the java program, which you can then create hardware which you can emulate.