PicoZ80 is a Drop-in Replacement for Everyone’s Favorite Zilog CPU

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The Z80 has been gone a couple of years now, but it’s very much not forgotten. Still, the day when new-old-stock and salvaged DIP-40 packaged Z80s will be hard to come by is slowly approaching, and [eaw] is going to be ready with the picoZ80 project.

You can probably guess where this is going: an RP2350B on a DIP-40 sized PCB can easily sit on the bus and emulate a Z80. It can do so with only one core, without breaking a sweat. That left [eaw] a second core to play with, allowing the picoZ80 to act as a heck of an accelerator, memory expander, USB host, disk emulator– you name it. He even tossed in an ESP32 co-processor to act as a WiFi, Bluetooth, and SD-card controller to use as a virtual, wirelessly accessible disk drive.

The onboard ram that comes with an RP2350B would be generous by 1980s standards, but [eaw] bumped that up with an 8 MB SPRAM chip–accessed in 64 pages of 64 kB each, naturally. If more RAM than a very pricey hard drive wasn’t luxury enough, there’s also 16 MB of flash memory available. That’s configured to store ROM images that are transferred to the RAM at boot– the virtual Z80 isn’t grabbing from the flash at runtime in [eaw]’s architecture, because apparently there are limits to how much he wants to boost his retro machines.

[eaw] has the PCB fab do all the fiddly assembly these days. Earlier versions were hand-soldered to his credit.
There are already drivers to use in certain Z80 systems. You can of course configure it as a bare Z80 with no machine-specific emulation, or set up the picoZ80 with the “persona” of a classic Z80 machine. So far [eaw] has tried this on an RC2014 homebrew computer, as well as Sharp MZ-80A– which we’ve seen here before, in miniature–and Sharp MZ-700. The Sharp drivers are still works in progress, after which the Amstrad PCW8256/Tatung TC01 is apparently next. We’ve seen Amstrad PCWs here a time or two as well, come to think of it.

If somehow you missed it, the venerable Z80 only hit EOL in 2024, so supplies won’t be drying up any time soon. This hack is really more about the quality-of-life addons this allows. Come back in a decade, and we’ll see if the RP2350 lasts longer than the stack of NOS Z80s.



from Blog – Hackaday https://ift.tt/3G5gcCv

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