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Ask Max: Is my 1.8GHz G5 Power Mac PCI card compatible with 5 volt PCI cards?

Asked on 03/08/2010:


I have a June 2004 model dual 1.8GHz G5 that I have gotten a trade in quote for because I have been unable to get it to work with an PCI interfaced A/D converter. After two years and several hundred dollars I discovered that this may be because I have 3.3 V PCI slots that are "designed to PCI-X 2.1 specifications", according to Apple. Which seems to mean that I have slots shaped like PCI-X slots but they only work with PCI cards (33Mhz 3.3 V,32 bit or 64 bit).

The company that manufactures the converter offers a PCI, PCI-X, and PCI-E version, but the PCI version does not fit and the PCI-X fits, and is recognized by the computer, but does not work. Instead of trading in my entire computer is there anything that can be done to my current Mac to remedy this problem?

The other option I am looking into is building a new PCI card with a pin configuration that will work in my current slot, but if you guys have a more attractive I would love to hear it because I am not terribly thrilled with how much of a headache this would be, granted it would be a smaller one than the past two years that I've spent trying to figure out what the problem was.

Thank you,



The G5 Power Mac series did have restrictions on the PCI voltage that it supported as described in this Apple article on G5 PCI Cards.

Another limitation of the PCI slots in the entry level G5s, like your dual 1.8GHz model, is that it does not have PCI-X, just the 3.3 Volt PCI support. I bet that the PCI version of the card needs 5 Volts to operate and the PCI-X version will not dumb down to PCI.

Even if you hacked your 5 V PCI card into the 3.3 V slot, it probably will not get the proper power to operate. Your best option would be to trade in that G5 for the next model up that supports PCI-X and use the PCI-X version of the card in your new system.

- Jacob

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