5 ms·

I have fond memories of the IRQ from the mouse card. It was the only source of regular interrupts you could get on the Apple II (that I'm aware of). So in 1987,

I have fond memories of the IRQ from the mouse card. It was the only source of regular interrupts you could get on the Apple II (that I'm aware of). So in 1987, I tried to write a preemptive switcher, so you could run two code paths at the same time. The development of that code was very painful. At the time, there was no external debugger. The moment you enabled the interrupt, your interrupt handler would get called, and it would try to program a context switch (something the 6502 is definitely not supposed to do). If you had any bug in there, your Apple II would be completely frozen, all you could do is reboot, and try to guess what went wrong and try again.

deater 1y ago
you can also get a regular interrupt from a Mockingboard sound card, these days it's probably more likely people will have one of those (especially if they are running under emulation) than a mouse card. when writing demos and games that have mockingboard support it's always tempting to take advantage of the timers on the 6522 chips on it, though it does mean that the programs wouldn't have been useful for most people back in the 80s/90s
geocar 1y ago
Fun. Mind if I ask what you were preemptively doing? If you ever get a time machine: The SSC could make an interrupt. So could the Microsoft card. There was also something called the Thunderclock card that could do like 100hz.