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#pc-hardware

2 posts

FreeDOSDeep Dive October 3, 2026 6 min read

PC 8259A PIC Delivery: IRQ Mapping, Cascades, Masks, and EOI

Trace legacy PC hardware IRQs through the 8259A PIC, including AT cascade mapping, masks, in-service state, and safe end-of-interrupt handling.

#freedos#pc-hardware#interrupts

FreeDOSDeep Dive October 3, 2026 7 min read

Understand legacy PC PIT channels, control/data ports, IRQ0 ownership, and why DOS applications should not reprogram the system timer casually.

#freedos#pc-hardware#timing