Tom Jennings' Friendly fZ80, an Emulated Digital CP/M and MP/M Z80 Machine, Goes Up for Sale

Tom Jennings has opened orders for the first production units of the Friendly fZ80, an all-new development machine designed for those looking to experiment with Digital's classic CP/M and MP/M operating systems on an emulated Zilog Z80.

"Friendly fZ80 is a completely self-contained [Digital] CP/M and MP/M computer. No modern computer is needed to use it," Jennings explains of the boxy metal machine, a compact throwback to the minicomputers and microcomputers which inspired its creation. "These are all-new design and new construction (emulated) [Zilog] Z80 computers that run CP/M version 2.2 and MP/M II version 2.1, the final version of Digital Research's preemptive multitasking-operating system."

Crack open the casing of a Friendly fZ80, and you won't find a now-discontinued Zilog Z80 nor even a second-source compatible. Despite its retro styling, the machine is built around modern hardware: a PJRC Teensy 4.1, with a 600MHz microcontroller core used to emulate a Z80 core running at speeds of up to 70–100MHz — an order of magnitude or two faster than the machines Digital was working with when CP/M and MP/M were fresh and new.

The microcontroller is used to emulate other hardware, too, including a floppy disk controller that uses full-size SD cards as removable media while an internal microSD works as two or three hard disks. In addition to the two operating systems, the machine comes loaded with a range of period-appropriate software.

For those used to CP/M, which was famously used as the "inspiration" for what would become Microsoft's smash-hit MS-DOS, MP/M may prove a surprise. "MP/M splits the screen into four independent windows ('consoles') each of which can simultaneously and independently run a CP/M or MP/M program. Windows can be resized at any time via keyboard functions," Jennings says of the multitasking OS.

"In its day, MP/M never got the chance to be as well-rounded by users as CP/M got to be; the then-new [Intel] 8086 IBM PC and competitors relegated MP/M a dead end curiosity. But it's fairly amazing software, maybe the most sophisticated code ever written for the 8080. I'm actively writing MP/M software now. I'm find[ing] it fairly easy to write code for, if a little stark, given the limited community. I'm hoping this batch of 25 machines will help grow developer and user interest in MP/M."

The shift from prototype to production has, however, seen a considerable increase in the price of the machine. When Jennings opened orders for pre-production prototypes back in November last year, early adopters were charged just $90; the maker expected that the final production would cost even less, if assembled in 50–100 unit quantities.

A smaller-than-hoped 25-unit initial production run coupled with ever-increasing parts and production costs, though, means that these first units are priced at $250 each including bundled software and a printed user guide. Buyers will have to provide their own USB Type-C power supply, keyboard, and a monitor with a VGA input capable of 1024×768 or higher.

Interested parties can read more about the project on the official website, or place an order for their own Friendly fZ80 on eBay.