What is a PCI-e Switch card used for?

Hi guys,

I was hoping someone could help me.

I've just purchased a Sapphire Crossfire 790gx motherboard, Phenom II x4 955, a Sapphire ATI Vapor-X 4890, along with many other brand spanking new components. I've not had to build a PC in a fair few years, and am totally confused as to what the PCI-e Switch card is for - it came with the 790gx motherboard.

Reading the manual, it says, "Install Switch Card to PCI-Express2.0 x16 graphics slot can double PCI-E X16 VGA card installed transfer rate up to 16 lane; 16Gbyte/sec."

That is complete gibberish to me. If someone could tell me when and why to install a switch card in the 2nd PCI-E slot I would be really grateful. My initial reaction is I should install it when not running 2 cards in Crossfire so that one slot is X16?

But some clarification wouuld be great. :telephone:

Many thanks,

Wells

i have an ASRock mobo that has some kind of a crossfire daughter card that switches the lanes from 16x to 8x. I think you probably have something similar. basically there is a card that, depending on which side u insert it, will change the lane configuration from 16x in one slot to two 8x slots. it's just a manual switch for changing the pci-e lane configurtions that most motherboards nowdays do automatically. however my card had it's own distinct connector that sits underneath my gpu ie it doesn't take up a pci-e slot. im not sure why yours has to be inserted into the pci-e, but in all cases i would trust the manual and just do it. it doesn't sound like a critical component that could fry your build anyway :P

Ok, having looked at the manual, I can see what its for.

The "Switch card" is a slot terminator.

You put it in the 2nd PCI-e 16x slot to disable it and make the 1st slot use all 16 lanes.

Quote:

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Two PCI-Express2.0 x16@8 lane graphic slot offer 4Gbyte/sec data transfer rate at each relative direction and up to 8Gbyte/sec concurrent bandwidth at full speed.

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Looks to me like the default set up is to have the 2 PCI-e slots in a split 2 x 8 lane configuration, ie Crossfire mode.

If youre only using 1 card, put in the Switch and youll get all 16 lanes for your 1 card.

Winner :rockon2:

Cheers for the help guys.