An 8-bit computer designed and built from scratch on breadboards, featuring 1MB of RAM and a VGA-compatible
This is an 8-bit computer built on breadboards from 7400-series logic chips.
It has 20-bit memory addressing and 8-bit-wide data paths.
- 20 breadboards
- Around 70 ICs, all 74HCxx series except for 2x AS6C4008 512Kx8 SRAM, 2x SST39SF040 512Kx8 flash,
and one 74AHCxx chip
- Numerous LEDs displaying the internal state of the CPU (although some of these were removed later on
- ~250 feet of 22 AWG solid-core wire, plus some jumpers
- Total materials cost of around $150
- Non-pipelined operation with two clock cycles (fetch and execute) per instruction
- 512K x 16 bits flash memory, 512K x 16 bits RAM
- Multiple addressing modes
- Six ALU operations: add with carry, and, or, xor, rotate right, and compare
- 1.5 MHz stable clock speed
- Flexible expansion boards, configured with a VGA board, PS/2 keyboard input, and an extra timer
- 9 breadboards
- A lot of ICs, mostly 74Fxx series with some 74HCxx series and one AS6C1008 128Kx8 SRAM
- Nearly 150 feet of 22 AWG solid-core wire
- Exactly one LED
- 640x480 color VGA output via a standard VGA connector
- 80x60 grid of characters (128x128 in memory)
- Up to 256 characters, 8x8 pixels each
- 16 colors (RGBI); two can be selected (foreground and background) per character cell
- Pixel-level scroll registers for both X and Y
See v3/ for full schematics of and the PCB design for the main CPU.
The VGA board is documented separately here.
Most notably includes a Z-Machine for playing a wide variety of text adventure games.
Homebrew CPU ring