Guy Makes His Own CPU, Running at 2Mhz, can be overclocked!

BMOW 1 borrows liberally from other homebrew designs, as well as the MAYBE design presented in the book Computation Structures by Stephen Ward and Robert Halstead. Data busses are 8 bits wide, and the address bus is 24 bits. Four 8-bit registers are used for general data, and three 24-bit registers store the program counter, stack pointer, and a scratch/working address pointer. Registers and the arithmetic and logic unit are interconnected by one data bus, while RAM, ROM, and memory-mapped hardware devices use a second data bus. The ALU also has dedicated left and right data input busses.

Machine language instructions are implemented as a series of micro-instructions, stored in three parallel ROMs to create a 24-bit microcode word. One micro-instruction is executed each clock cycle, and the micro-instruction bits are used directly as enable and select inputs to control all the chips in the machine. Up to 16 micro-instructions may be needed to implement a single machine language instruction.

* Current clock speed is 2MHz. It could theoretically go to about 3MHz (untested).
* 512 KBytes of RAM, 512 KBytes of ROM.
* Power draw is 10 Watts, 2.0A at 5V.
* VGA video output is 512×480 with two colors, or 128×240 with 256 colors.
* Audio and music is provided by a three-voice programmable sound generator.
* Keyboard input is a standard PC keyboard with PS/2 connector.
* Debug display is a 24×2 character text LCD.
* There are roughly 1250 wires connecting the components, so 2500 individual hand-turned wire wraps.