NVIDIA's shady trick to boost the GeForce 9600GT

[Luka_Aveiro]

Guys, you haven't realized yet this has nothing to do with linkboost...

It has to do with PCI-Express frequency, once techpowerup considers PCI-Express frequency/4 is the clock generator for gpu frequency, as 100mhz/4=25mhz, that should be a regular crystal clock generator, but that doesn't exist on the 9600GT!!!!

When looking at the PCB, the only crystal we could find is a 27 MHz one, so where is the magical 25 MHz coming from ?

As many of you know, the PCI-Express bus clock frequency which connects the card to the rest of the system is running at 100 MHz by default. What NVIDIA did is to take this frequency and divide it by four to get their reference frequency for the core clock.

On systems where the PCI-E bus runs at 100 MHz, this results in the 25 MHz used for the default clock indeed. But once the PCI-E clock is increased beyond that, the GPU will magically run at higher clock speeds, without any changes to the graphics configuration, BIOS, driver or any software.

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!

So, taking their example: 725mhz/25mhz(clock generator powered by pci-express@100mhz)=x29;
If PCI-Express Frequency= 110mhz-> 110:4=27,5; 27,5x29= ~798mhz

Let's take it to stock clocks:
650/(100/4=25)=x26
(110/4)=27,5; 27,5x26=715mhz

So, 715-650=65; 65=10% of 650
So if you increase PCI-Express by 10%, you will increase your core clocks by 10%.

I wish I had a 9600GT in my hands to confirm this, it just seems too good to be true