jmke

On "normal" VGA cards, when you increase the PCI-Express bus frequency you increase the theoretical bandwidth available between card and the rest of the system, but do not affect the speed the card is running at. On the GeForce 9600 GT, a 10% increase in PCI-Express frequency will make the card's core clock run 10% faster!

http://www.techpowerup.com/reviews/N...9600_GT/1.html

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jmke

This can cause problems if you have a factory overclocked sample, since the OC'ed PCIe bus will increase the GPU speed further still, you can have VGA problems, and since you dont know PCIe <> GPU speeds are linked, you'd think that the VGA card is the culprit and you will RMA it.

Geoffrey had two samples showing this behavior, their factory OC was already far beyond reference speed, the extra PCIe boost pushed them over the edge of stability. With no official info about this hidden "boost" we expected the VGA to be broken; but in fact, it was an overclocked PCIe bus which caused the problems...

undocumented features like this should be made public by NVIDIA in my humble opinion to prevent these issues

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Kougar

Why is it being considered a "feature"? IIRC the PCIe bus is limted to about 115Mhz, past that and things stop working just like with PCI. SATA drives and some Gbit chips use the PCIe bus.

For normal cards overclocking the PCIe bus does nothing as far as performance goes.

jmke

undocumented dependencies on other system component speeds is more correctly put

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Kougar

Exactly. A "feature" is somethng of beneficial value to the user. This is anything but.

geoffrey

I had PCIe at only 110MHz, even that caused problems on the videocard. Yes, in common pc this hidden feature will not cause issue's, but just think about all those we don't have a common pc