commodore-pet-clone

Note: The latest information on this project is here.

PET Clone

Open hardware clone of the Commodore CBM/PET using modern parts. Some assembly required. :-)

Status

Working prototype. PCB and SMT manufacturing files are here.

About

This open hardware CBM/PET clone can be used in two ways:

1. By itself with an HDMI display and USB keyboard
2. As a mainboard replacement to repair/enhance a vintage CBM/PET

You can also do both at once, as shown in the image below:

Design

The following block diagram provides an overview of the system architecture:

Here are the highlights:

• CPU and I/O are similar to the original Commodore design, using the 6502, PIA, and VIA.
• Main RAM, Display RAM and ROM are combined on a single 128K SRAM.
  • On POR the MCU initializes $9000-FFFF with the user's selected ROM set
  • After initialization, $9000-FFFF is write protected.
• Timing, address decoding, and native PET video are consolidated on a small FPGA.
• The MCU reads display RAM and mirrors the PET video to HDMI (via bit-banged DVI)
• The MCU also reports USB keyboard input to the FPGA
  • The FPGA intercepts reads from $E812 to inject USB key input as-needed
  • When no USB keys are pressed, the read passes through to PIA1.

Contributing

Collaborators warmly appreciated (see Issues).

License

This project is public domain under the CC0-1.0 license, exempting portions incorporated from other open source projects as noted here and in the source code.