Andre Fachat has created a CPU add-in card for Commodore PET machines. “It speeds up your PET to up to 12.5MHz (at least that’s the plan for the final stage, but it currently looks good!). The board uses a 65816 CPU that runs at up to 12.5MHz, plus a Xilinx CPLD as logic glue. It includes up to 1MByte fast RAM (run at CPU speed) plus 512k parallel Flash ROM, that can be used as boot ROM”. Source code and schematics are provided. Via Commodore News Page.
I’m all for the “because we can” reasoning, but really? The only possible use for the PET in my opinion is for nostalgia, not performance modding. Seems like the C64 community is a lot more useful for tweaking/performance modding the 6502, etc. Even new mods on the C64 seems a little pointless today.
Way back in “the day” I installed a 65816 upgrade in my Atari 130XE, which was sold as the DataQue Turbo816. It included a replacement OS written in 16-bit code, which made even standard 8-bit code run faster. Mostly good for geek cred, but being a bit faster didn’t hurt.