8259 PIC: Difference between revisions

8259 PIC (view source)

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PIC is managed by the kernel, not the OS; and by the way Linux isn't an OS, it's a kernel (GNU/Linux is OS)

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Revision as of 11:30, 3 May 2020 (view source) osdev>Nero No edit summary ← Older edit		Revision as of 12:40, 30 June 2021 (view source) osdev>Akibazmain (PIC is managed by the kernel, not the OS; and by the way Linux isn't an OS, it's a kernel (GNU/Linux is OS)) Newer edit →
Line 251: The correct way to handle an IRQ 15 is similar, but a little trickier due to the interaction between the slave PIC and the master PIC. First check the slave PIC chip's ISR to see if the IRQ is a spurious IRQ or a real IRQ. If it is a real IRQ then it is treated the same as any other real IRQ. If it's a spurious IRQ then don't send the EOI to the slave PIC; however you will still need to send the EOI to the master PIC because the master PIC itself won't know that it was a spurious IRQ from the slave. Also note that some ~~operating systems~~kernels (e.g. Linux) keep track of the number of spurious IRQs that have occurred (e.g. by incrementing a counter when a spurious IRQ occurs). This can be useful for detecting problems in software (e.g. sending EOIs at the wrong time) and detecting problems in hardware (e.g. line noise).