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A comment on Show HN: Apple II clock using interrupts from physical pendulum clock.

Re:Show HN: Apple II clock using interrupts from physical pe... by kazinator on Sunday January 28, 2024 @01:43PM (#39168544)
Wow, people are still working on the problem of the Apple II not having an RTC, in some shape? :)

Say, weren't there some issues with interrupts on the Apple II, due to both the 6502 as well as buggy ROMs? Basically, none of the I/O in the stock system with Apple parts used interrupts whatsoever. Not disks, not serial communication.

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Re:Show HN: Apple II clock using interrupts from physical pe... by thought_alarm on Sunday January 28, 2024 @02:32PM (#39169012)
The problem with the original firmware was that its interrupt handler used a zero-page location to store the accumulator. AppleSoft BASIC uses the same zero-page location for its own use, which makes BASIC incompatible with interrupts.

Another problem was with in the original Apple IIe. Its firmware interrupt handler was not updated to handle the new auxiliary memory and 80-column video configurations.

ProDOS provided proper support for interrupts, even on older Apple IIs (needed for mouse-based GUI apps and realtime clocks), and the firmware was eventually updated in the IIc and Enhanced IIe.

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Re:Show HN: Apple II clock using interrupts from physical pe... by wkjagt on Sunday January 28, 2024 @02:00PM (#39168711)
Yeah I think nothing actually uses interrupts by default. But they're accessible through the expansion ports. Not sure what the problem would be though.
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Re:Show HN: Apple II clock using interrupts from physical pe... by noxon on Sunday January 28, 2024 @02:02PM (#39168740)
Serial interfaces could use interrupts, and it was necessary at higher baud rates.
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Re:Show HN: Apple II clock using interrupts from physical pe... by tonyedgecombe on Sunday January 28, 2024 @02:08PM (#39168811)
Yes, I remember writing a print spooler using interrupts as part of my first job.
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