7 hours ago
- A 16-bit serial homebrew CPU was built using only 8 ICs, including memory and clock, achieving Turing completeness.
- The CPU uses a single EPROM as both control state machine and 1-bit ALU, with two serial SRAMs and one serial FLASH.
- It executes around 12,000 instructions per second at up to 10 MHz, capable of streaming video on a Nokia 5110 LCD at ~10 FPS.
- The architecture minimizes chip count by shifting data processing into the control memory and using serial operations for 16-bit values.
- Key components: EPROM (control + ALU), 74HC574 (output latch), 74HC595 (instruction buffer), 74HC393 (microcode counter), two 23LCV512 SRAMs, one W25Q80 FLASH, and a 74HC14 clock generator.
- The instruction set includes 52 operations (most 16-bit) with arithmetic, branching, memory access, and I/O, though no self-programming is possible.
- Performance is limited by propagation delays; actual stable clock is 10 MHz despite calculated 4.6 MHz limit.
- Potential improvements include faster binary counter, EPROM with more address lines, and additional instruction fetching bandwidth.
- The CPU can drive a PCD8544 LCD, produce 8-bit audio, and interface with SPI devices like a DS1302 RTC, but 3D graphics are very slow.