Open hardware clone of the Commodore CBM/PET using modern parts. Some assembly required. :-)
Working prototype. PCB and SMT manufacturing files are here.
This open hardware CBM/PET clone can be used in two ways:
- By itself with an HDMI display and USB keyboard
- As a mainboard replacement to repair/enhance a vintage CBM/PET
You can also do both at once, as shown in the image below:
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.
Collaborators warmly appreciated (see Issues).
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.
