[sci.electronics] Interrupt conflicts

kthompso@uceng.UC.EDU (ken thompson) (08/21/89)

A friend of mine recently took his PC AT clone back to the clone
shop for warranty repair.  He was told that he would have to 
buy a new  mother board.  The owner said he damaged it by having
two cards set to the same interrupt, IRQ 4. This PC also had a 
hard disk failure a couple of weeks earlier and the replacement
hard disk was also cooked with the mother board. Now this guy
won't give back the PC, not even the cards in it that were not 
purchased there.  He says he may need it for evidence.

I say that IRQs did not cause this.  More likely an over voltage
condition by the power supply.  The mother board IRQ chip is 
just a TTL input waiting for a high. What does it care how
many highs are put on the IRQ line.  I could see where the conflicting
cards could blow out one another but not the mother board.  I have
tried this myself on an XT.  The only problem was with software
not working correctly.

My friend has a lawyer working on this but how does he prove that IRQs
did not blow up his mother board and two hard disk?  Any suggestions
will be greatly appreciated.

Thanks in advance. 


-- 
Ken Thompson				University of Cincinnati
					Dept. of Chemical Eng.
					kthompso@uceng.uc.edu