> In any case, I did not find the protected mode.
Because, unless I'm misunderstanding the video, it doesn't exist until you add a whole bunch of external hardware (which is why the video is clickbait - a fact he acknowledges later.)
Because, unless I'm misunderstanding the video, it doesn't exist until you add a whole bunch of external hardware (which is why the video is clickbait - a fact he acknowledges later.)
https://en.wikipedia.org/wiki/Kludge
It's on display at the Paul G. Allen Living Computer Museum.
https://sites.google.com/site/mthompsonorg/Home/pdp-10/pdp-1...
https://donhopkins.com/home/catalog/images/mc-console.jpg
Lars Brinkhoff has taken photos of the KL-UDGE blinken lights panel and naked wire wrap boards:
https://twitter.com/larsbrinkhoff/status/1128601896619524097
>Photo 6/7: KL-UDGE lights panel
>Photo 7/7: KL-UDGE boards. Real-time time of day clock?
Was a pretty popular machine - sold 5.7 units worldwide. But probably only a tiny fraction actually used the CP/M mode that used the Z80.
The Tiki-100 is an obscure Norwegian 8-bit computer from 1984, also Z80-based. It had nice graphics for its time, with 16 colours from a 256-colour palette. However, it was very hard to use productively, since the machine had no video sync interrupts.
What the guys in the demogroups figured out, was that it did have parallel port interrupts, and with a tiny hardware mod (just a wire from the expansion port to the parallel port), they could "steal" those for Commodore 64-style raster interrupts.
That it wasn't something usual with microcomputers of the time wasn't because it would have required some uniquely clever design. Rather it had to do with them being single-user/single-task, with simple operating systems where programs were expected to have full access to the machine.
A common use for multitasking in the 8-bitter era was print spooling; it was very inconvenient to have to wait for your document to finish printing before you could continue editing! People frequently bought external hardware printer spooler boxes to connect between their computer and printer because of this. Similarly, duplicating floppies was pretty inconvenient because you couldn't do anything else while it was happening, even if you had four floppy drives like I did, with literal megabytes of storage space available to read porn or play video games while the floppies were copying.
Historically on larger machines it was also common to use multitasking to overlap very slow disk I/O with useful computation. (The alternative is to use asynchronous I/O and write your program as an event loop, like a game or Node.js, or to do your I/O from interrupts, which is close to multitasking.) In theory this could have been useful on 8-bit micros as well but I don't think I saw any cases of it actually happening.
Why mind this if the hardware to add is the same level of technology like Z80 itself? I would be glad to build a computer as advanced as possible combining some Z80s and additional HW.
But it's not "the Z80's protected mode" - it's "the Z80 + an extra circuit to emulate protected mode". It's a super clever hack, yes! But filthy clickbait also.