Confusion on IRQs

falcon2099

Could somebody please spell this out for me. I've seen different sources list different functions for IRQs.

As far as I can deduce these are correct:

IRQ0 -System Timer
IRQ1 -Keyboard
IRQ2 -Cascaded to IRQ9
IRQ3 -Serial port (COM2/COM4)
IRQ4 -Serial port (COM1/COM3)
IRQ5 -Parallel port 2 (Sound card or LPT2)
IRQ6 -Floppy drive
IRQ7 -Parallel port 1 (LPT1) (available if no local printer present)
IRQ8 -Real-time (CMOS) clock
IRQ9 -Cascaded from IRQ2
IRQ10-USB (available if no USB present)
IRQ11-SCSI (available if no SCSI present)
IRQ12-PS/2 mouse (available if no PS/2 mouse present)
IRQ13-Math coprocessor
IRQ14-Primary IDE controller
IRQ15-Secondary IDE controller (available if no Secondary IDE controller present)

Thanks to all!

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Comments

ScarletLace

What you have listed seems correct to me. IRQ 10 and 11 are usually available and can be used for SCSI controllers, PCI cards or just about anything.

I think maybe the reason it's confusing is that some books list it the way the IRQs are been used in real life in addition to how they are designed to be used. For example, even though the 2nd IDE channel is usually used and designed to be used with IRQ 15, in practice some people have tried to use it with IRQ 10 and it has not produce any conflict in their system, so in a case like that, the book might list the 2nd IDE channel under other common uses for IRQ 10 even though IRQ 15 was designed for the 2nd IDE channel(this is true for the A+ Complete book by David Groth which is the textbook that I use).

dbjjones

Those are listed in order. If you are having trouble remembering them,
what I did is make up some flash cards. Now I have them planted in my
head.

skully93

This is one of those odd things that still lingers. Most people will never manually assign an IRQ these days, so anyone under 25 has a harder time with it. It drove me nuts when I took the A+ because even though I had done it, it had been a long time and I don't remember them anymore.

Just memorize them and know what they're for, and you'll pick them right up again if you need 'em.

sys_teck

ok here is good site i found about "how DMA and I/O, IRQ work.

http://www.millbury.k12.ma.us/~hs/techrepair/IRQ.html

may it will help

falcon2099 wrote:

Could somebody please spell this out for me. I've seen different sources list different functions for IRQs.

As far as I can deduce these are correct:

IRQ0 -System Timer
IRQ1 -Keyboard
IRQ2 -Cascaded to IRQ9
IRQ3 -Serial port (COM2/COM4)
IRQ4 -Serial port (COM1/COM3)
IRQ5 -Parallel port 2 (Sound card or LPT2)
IRQ6 -Floppy drive
IRQ7 -Parallel port 1 (LPT1) (available if no local printer present)
IRQ8 -Real-time (CMOS) clock
IRQ9 -Cascaded from IRQ2
IRQ10-USB (available if no USB present)
IRQ11-SCSI (available if no SCSI present)
IRQ12-PS/2 mouse (available if no PS/2 mouse present)
IRQ13-Math coprocessor
IRQ14-Primary IDE controller
IRQ15-Secondary IDE controller (available if no Secondary IDE controller present)

Thanks to all!