MCLZ8 – Zilog Z80 Emulator in TRS-80 Model III

Update: Preliminary results indicate that the MCLZ8 is more than 15 times faster than the stock Z80 in the TRS-80 Model III. Stay tuned…

My latest project, the MCLZ8, is a Zilog Z80 emulator which can be used as a drop-in replacement for the original Z80. It uses a Teensy 4.1 microcontroller board which contains an 800Mhz microcontroller and a small PCB to perform the voltage translation between the motherboard and the microcontroller. The MCLZ8’s Z80 emulation passes the exhaustive ZEXALL opcode test suite and the speedy microcontroller allows the ability to simultaneously mimic the Z80’s local bus interface.

The MCLZ8 seems to work quite well as a Z80 replacement in a TRS-80 Model III where it runs BASIC and is able to boot from the diskette drive. I have tried NEWDOS and a number of games and I will test more applications in the near future.

Of course the next step will be to see how much acceleration we can achieve! 🙂 If we eliminate cycle-accuracy, locate the RAM and ROM into the MCLZ8’s internal RAM and access them at the top speed of the microcontroller we should get some very interesting results! There have been a number of TRS-80 accelerators over its history, so it will be interesting to see where the MCLZ8 ranks!

But for now I am happy to see the MCLZ8 working inside of this legendary computer!

MCLZ8 – Zilog Z80 Emulator in TRS-80 Model III