Can I use a 6 pin PCIe connector in an 8 pin slot?

Are the two types of PCIe power connectors electrically compatible? The 6 pin connector will physically mate with an 8 pin slot I just don’t know if it’s a fertile relationship.

I realise that cards with an 8 pin connector typically require more power than a 6 pin connector can provide but there are some cases where it can provide enough power provide the card isn’t over-clocked.
Also I’ve seen Sapphire cards with an 8 pin socket that include a dual Molex to PCIe 6 pin cable which suggests that it may work.

In most cases, yes. It depends on the card though.

Yep you hit the nail on the head. No overclocking but it should work :)

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Originally Posted by aidanjt

In most cases, yes. It depends on the card though.

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Thanks. It’s a HD 2900 GT 256MB which is a bit of a power hog – Saphhire.

All that the extra 2 pins are, are two ground connections. It basically tells the GFX card that the PSU and cables are rated to supply upto 150w down that cable.

Which gfx card are you looking at? On the older cards they were designed to give extra juice for overclocking, but I would be careful on newer cards. As it may end up pulling too much power through the mobo and PCI-E 1.0 is only rated for 75w.

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Originally Posted by Cuervo

Thanks. It’s a HD 2900 GT 256MB which is a bit of a power hog – Saphhire.

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you posted while I was typing, lol. At the bottom of the link you posted, under system requirments it says it will work with a 6 pin but overdrive (Overclocking) is disabled.

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Originally Posted by Cuervo

Thanks. It’s a HD 2900 GT 256MB which is a bit of a power hog – Saphhire.

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Then yes, you'll be fine, the HD2900 only uses the 8pin to providing a safe amount of overclocking juice.

Thanks for all the quick and eloquent replies. I’m a newbie around here and really impressed with the quick responses. Cheers. :)

Yup, I'm using a 6 pin on my 2900gt. I can still control the fan and overclock with ATI tray tools (beta version), and have also tried ATI tray.
See THIS thread for more info about the 2900gt and fan control