Cromemco ZPU Board with a 4 MHz Z-80A

I’m not promising a picture every day, but I might throw one in as I think about.

Today’s picture is of a Cromemco ZPU board featuring a 4 MHz Z-80A microprocessor for the S-100 bus architecture.

Cromemco ZPU Board


This board has no memory, no input or output capability, no video capability, no sound or anything else.

It does have a red switch in the upper-left part of the board near the heat sink that will toggle the system between 2 MHz and 4 MHz. Just like the “turbo” switches on the early PC-clones, dropping to 2 MHz allowed for better compatibility with slower hardware and software designed for the original Z-80 that only ran at 2 MHz.

As a quick refresher, 2 MHz = 0.002 GHz.

One more thing: it’s single core, too!

For those interested, you can view a catalog of Cromemco products on The Computer Archive at