5 ms·
Using the NMI (non-maskable interrupt) on an Apple II is so wrong! The disk software relied on precise timing of instruction sequences to read and write bits on
by tlb 7y ago
Using the NMI (non-maskable interrupt) on an Apple II is so wrong! The disk software relied on precise timing of instruction sequences to read and write bits on the disk. If you have interrupts going, reads will fail and writes will corrupt the sector being written and possibly the next sector.
- sehugg 7y agoYeah, with just a XOR checksum this would be pretty dangerous even for reads. Of course, in those days you could probably sell someone a $50 FIFO buffer to work around the disk controller problems :)
- Narishma 7y agoIt's mentioned in the article.
- derefr 7y agoI feel like the article is written from the perspective of an embedded software/hardware appliance developer, or the hobbyist equivalent. It makes a lot of sense to talk about saving $100 on an RTC board if you only want a clock to for some one-off script you’re writing. Things can be as fiddly as you want in that case—e.g. load the program from disk to memory, then enable the clock using the little switch you built into it and let it tick while the disk is spun down.