From: "Roberto Safora" :Sent: Tuesday, September 26, 2000 2:58 PM
Subject: [PCBUILD] changing pci slot


> In a conversation some of my partners said they have had this problem:
> Trying to instal a  PCI network card, they have troubles that dissapeared
> when they put the card in a different PCI slot. It ocurred with different
> motherboards marks and with different cards mark( Shuttle, Aopen, DTK for
> mobos and Planet, Aopen, 3com for NIC.
> ¿?
> TIA
> Roberto
>

Roberto,

PCI slots, the AGP slot and onboard USB controllers share 4 IRQ's.   How
these slots and controllers share the IRQ's depends on the motherboard
manufacturer.  This information is usually found in the motherboard manual
or from the maker of the PC.    Many network cards don't like to share an
IRQ or prefer to be on the higher IRQ's like 10 or 11.  Changing the slot
the card is located in can change the IRQ assigned to the card and also
changes what other slots may or may not be sharing the IRQ.   As an example,
an Abit BE6 motherboard shares IRQ's as follows:

AGP slot and PCI slot 1 share an IRQ
PCI slot 2 does not share an IRQ
PCI slot 3 does not share an IRQ
PCI slot 4, PCI slot 5 and the onboard USB controller share an IRQ

Many motherboard manufacturers allow you to set the IRQ assigned to PCI
slots in the BIOS, for cards that require specific IRQ's.  Careful placement
of the cards in the slots based on how a motherboard shares the IRQ's
between PCI slots, AGP slot and the onboard USB controller can help to
prevent conflicts that arise from cards that do not like to share IRQ's.

Hope this helps,

Mary Wolden

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