I’ve decided to collect these from the Internet to save time looking for them.

IEC Serial Port

• C64 – Wiki: Serial Port
• How the VIC/64 Serial Port Works: Compute! July 1983

The Video/Audio Output Port

Commodore 128 RBGI Port

VGA Pinouts

If you’re using the GGLabs CGA2RGBv2 board to convert the C128’s RGBI signal to analog RGB then the VGA Pinouts might be useful.

NOTE: Pins 5, 6, 7, 8, and 10 should all be connected to common ground (GND).

NOTE: Pins 4, 9, 11, 12, and 15 are not used and should be left unconnected.