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Implicit EOI
Posted: Sun Jul 01, 2012 10:03 am
by suslik
I wonder why in all examples I have ever seen people use explicit EOI, but the CPU disables all interrupts byitself (if we are using interrupt gate descriptor)? So, can I use implicit EOI or there are some pitfalls?
Re: Implicit EOI
Posted: Sun Jul 01, 2012 10:17 am
by JamesM
Hi,
The EOI is a signal to an external device - the PIC. The PIC is connected to the CPU via the CPU's interrupt (IF) line. It will hold that line (active-)low until an EOI is received - only at that point does it know that the CPU actually took and serviced the interrupt.
So no, you can't avoid the EOI.
Cheers,
James
Re: Implicit EOI
Posted: Sun Jul 01, 2012 11:06 am
by suslik
JamesM, you talk about explicit EOI, but I need to know about implicit EOI.
Re: Implicit EOI
Posted: Sun Jul 01, 2012 12:01 pm
by JamesM
suslik wrote:JamesM, you talk about explicit EOI, but I need to know about implicit EOI.
What I said was:
So no, you can't avoid the EOI.
As in, there is no such thing as an implicit end-of-interrupt.