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By this, I mean is it possible to put a PCI-X card in a PCI slot? I heard from someone (who deals with servers all the time) that this is the case, however I may have misheard. Also, the card DOES fit, I'm wondering if they're electrically compatible.

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up vote 9 down vote accepted

Yes, as long as the PCI slot is a 2.x or later, PCI 1.0 was 5v while PCI 2.x was 3.3v - which is electrically compatible with PCI-X.

Source: Wikipedia PCI-X

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Thank you! This helps a lot. Since PCI 2.0 was released in 1993, this pretty much means any PCI slot. – Eli Aug 12 '11 at 20:15
Just for future reference, the card in question was a Broadcom BCM5701, and it works in a normal pci slot as well as pci-x – Eli Aug 13 '11 at 0:23
Maybe this new question adds some interesting detail to the things?… – Sopalajo de Arrierez Nov 14 '14 at 2:59

That isn't backwards compatibility. Putting a PCI card in a PCI-X port would be considered backwards compatibility - which is the case, as long as it is PCI 2 as the voltage on PCI 1 is not the same. To sum it up, PCI 2 cards can be put in PCI-X ports, not the other way around.

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There are some PCI-X cards that are keyed in the same fashion as a PCI card and will work in a PCI 2.0 slot. The original question stated that the card does fit in the slot. – Dustin G. Aug 12 '11 at 20:25
PCI-X can go in to PCI slots by design. – Keltari Aug 15 '11 at 5:18
I have fixed the question title. – kinokijuf Feb 29 '12 at 17:44

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