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Rev

I know the 8259 best out of all the components mentioned here, but with my limited knowledge this answer rings the truest for me. Certainly I've studied the 586 architecture pretty well, and even have some experience (back in the before times) with an Amiga 3000UX with a 68030, what we might today call a rudimentary GPU, and asynchronous busses, and all I know tells me that the chipset used around a CPU has a huge impact in how the overall system works.
– Todd Wilcox
Commented Oct 17, 2020 at 3:57
1

Deactivating interrupts also allows for bit-banging I/O with well defined timing, and for deterministic response times when polling a port.
– Michael Graf
Commented Oct 17, 2020 at 10:36
1

@MichaelGraf ... while it kills any deterministic response times for everything else. Nothing comes for free.
– tofro
Commented Oct 17, 2020 at 12:43
2

Many home computers were used as hard real-time systems when doing home-computer tasks such as writing or reading data from/to tape or (on the Apple II series) disk. Even an unexpected one-cycle delay while writing a disk sector on the Apple II would totally corrupt all the data thereon.
– supercat
Commented Oct 17, 2020 at 16:53
I encountered an old product our company had that did hard-realtime work on MS-DOS. The built the realtime scheduler into the application.
– Joshua
Commented Oct 18, 2020 at 18:45

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