A modern Z80 Computer Front Panel

James Stanley has designed and built a generally applicable front panel for almost any Z80 system, if you can get to the relevant bus pins. For extra retro points he’s used design notes from a 1978 issue of Kilobaud magazine. There’s also a video, using the front panel with a modern rc2014 system:

… an excellent article in the June 1978 issue of Kilobaud Magazine. It’s the one starting on page 26: “Home-Brew Z-80 System … Part 1: front-panel construction”. Incidentally, the magazine is a fascinating read just for the products that are advertised in it, even if you ignore the actual content!

AIUI, the front panel uses M1 and WAIT to implement single-stepping, BUSRQ and BUSACK to get hold of the bus, then MREQ to inspect and modify memory or IOREQ to interact with I/O devices.

via Alan Cox on mastodon.

(See also @hoglet’s in-circuit emulator project , where much fun has been had trying to keep various z80 computers alive while their Z80 is paused.)


James put together 1200 lines of C to run a web server from his rc2014 - here it is, if it’s presently running. And here is the writeup. And here’s what it looks like:

It totals about 1200 lines of C, all of which was written on the RC2014 in the ZDE 1.6 text editor, and compiled with the Hi-Tech C compiler.

via D J Sundog on mastodon.

That’s great that he managed to get it to work, and that he did it using native tools on a native system (vs cross development).

Reading the article I wonder how much better his experience would have been using Turbo Pascal. Or, honestly, once he got started, just doing it in raw Z80 assembly.

I know TP doesn’t take 7 minutes to build a 1200 line program, and, since none of the native compilers were spectacular in their optimizations, I doubt the TP versions would have been dramatically slower. I wonder how much of his 7 minutes was linking rather than just compiling.

Imagine how long this would have taken with actual floppy drives instead of (probably) the solid state drives that he was using.

The issues with the TCP packet retransmission and memory space was very interesting.

Also, considering the 7 minute turn around, if folks ever wondered how something as “horrible” as BASIC ever got traction in the micro computer market, this is a key reason.

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Back when I was still working on Acorn User magazine, a colleague and a bunch of other lads were working on a commercial product that used compiled code on BBC micros (probably Masters, but memory is fuzzy). They had a rule that each time they compiled the code, they would spend the time indulging in a race. Still sitting in their office chairs, they had to propel themselves around the room. The winner was the one who was in the lead when compilation finished. It was, apparently, exhausting.

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