Simulating old microprocessors (and systems) with modern hardware

Happy 2021.

A few months ago I mentioned how the venerable 6502 could be simulated with an Arduino IDE compatible ARM board.

The results were a version of Commodore BASIC, which ran at an effective clock frequency of 48MHz with the ARM providing all system RAM, ROM and a serial interface.

Shortly afterwards I came across a PDP-8 simulator, complete with a ROM listing for FOCAL, which allowed a lunar lander game to be played - just like it’s 1969 again.

Over the last week, I found Jean Claude Wippler (Jeelabs) Z80 simulation, which started life on an STM32F103 and after a STM32F407 ended up on a 600MHz ARM M7 - the Teensy 4.0.

The simulated Z80 runs all the Zexall tests at a simulated clock of 158MHz - that’s 39.5 times the thoughput of the original Z80A.

Many of the classic microprocessors, micro and minicomputers are now readily simulated on very low cost hardware - The Teensy 4 is less than $20.

Jean Marc Harvengt has now ported several simulated systems to the Teensy 4.1


Quite recently Ted Fried reported on his MCL65+, also based on a Teensy 4.1 - with 600MHz available, aiming to emulate only the 6502 MPU, and bit bang the interfaces to drive a 6502 bus. Still a work in progress, I think.

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Ted Fried has made significant progress - the hardware side of this is nice and simple:

Two short videos, first of cycle-accurate speed, and then full-on speed: