Accompanying video: https://youtu.be/tMYGlYO3v9U?si=e0UUzCVyMtc6L2-L

Funniest 8080-era multitasker was made by Siemens in 1976. Instead of allocating memory from common RAM, they just switched small RAMs mechanically. You only needed to dump registers at each switch. Particularly economical in 8080 which is not good for indexed memory models like Z80.

Writing my own pre-emptive multitasker in Turbo Pascal on our x86 as a self-taught teenager was a core memory thing.

I recall spending a few days mulling over the exact sequence of instructions to save the state of the previous task without clobbering the flags or any registers.

The result was that I could register functions (procedures) as tasks with their own little stack, and it would switch preemptively between them in a round-robin fashion.

I'm not familiar with Z80 asm but from what I can gather ot looks very similar to what I had. I was running in real mode so also had very limited resources for each task, and z hardcoded upper limit on the number of tasks.

While I'm wildly more productive these days, I kinda miss how not having internet made accomplishments so much greater. It's like walking up a mountain on your own vs taking a tour bus to the summit.