On Mon, Apr 22, 2024 at 2:30 PM Paul Koning via cctalk <cctalk@classiccmp.org> wrote: > Anyway, I would think such a small microprocessor could emulate a PDP-11 just > fine, and probably fast enough. The issue isn't so much the instruction set > emulation but rather the electrical interface. That's what would be needed > to be a drop-in replacement. Ignoring the voltage levels, there's the matter > of implementing whatever the bus protocols are.
Emulating an F-11 chip or a J-11 chip is certainly possible with a modern MCU, just need TTL-friendly I/O. F-11 is 40-pins (and can have additional instructions added by adding microcode ROMs next to the CPU) and the J-11 is 64 pins on a fat chip carrier. > Possibly an RP2040 (the engine in the Raspberry Pico) would serve for this, > with the PIO engines providing help with the low level signaling. Sounds > like a fun exercise for the student. Could be a good start but would still need level shifters. J-11 runs at 15-18Mhz for an idea on how fast the bus implementation has to be. -ethan
