Note: Update here: This is my build of a 6502 retro computer using a design from by Daryl Rictor and improved by Rich Cini. Rich had a batch of PCB's made so I jumped on the chance to get one rather than having to wire wrap something. Here are links to Daryl and Rich's sites. Daryl Rictor's SBC 2.5: Rich Cini's SBC 2.7: This machine has 32 RAM, 32 K ROM, a 6551 UART, and 32 GPIO pins from the VIA 6522's. Ten of the I/O pins are used for the IEC port and SPI to the video chip. Which leaves a healthy number for robotics use.