Is it possible for a GPU to limit a CPU overclock?

Trying to work this thing out but to no avail. At stock everything I can take the CPU up from 2.93ghz to 3.25 dead stable and no problems at all with heat. But any further ie more than 296mhz fsb the laptop will freeze.
However then I discover that upping the PCI E frequency from stock which is 103mhz to say its stable max 112 allows OC of up to 3.5ghz. However at this speed the GPU will artifact even at stock clocks. Likewise if PCI E frequency is downclocked then GPU can be clocked higher but the CPU overclock becomes limited.

Can somebody shed some light on this, theoretically would say a 256bit card allow a higher CPU overclock?

 

No, I wider memory bus allow more data to be pushed through, it doesn't make data go faster. Are you sure it's not a chipset limitation?

 

The chipset should be good for at least 317-333mhz I guess it ranges widely, but personally with a e6600 I could hit 317.

 

The GPU is tied to the PCIe frequency. That will be your limiting rate in most applications. It's probably the memory controller on the GPU or whatever that isn't happy with the faster PCIe clocks. Overclocking your FSB (and therefore other system bus clocks) affects EVERYTHING connected to the bus. That can cause some major issues with various hardware. If you're seeing graphical artifacts, that means you've pushed the bus past where it should be for that GPU. A wider bus will not go any faster, it will just carry more data per clock. Your only option is to try multiplier overclocks on the CPU (if that's possible). You could damage many of your components if you insist on tweaking the bus speeds.

 

Thanks for the info Pitabred. Yeah I have never left the bus speed at 112mhz, was just testing the system to the edge as it were. Usually I operate everything at stock and just up the CPU to 3.25ghz when gaming or doing some photoshopping, multi OCing is impossible as the bios is very limiting like most laptops I use clockgen. So it seems the amount by which I could overclock on stock PCI E does depend on the card(8600M GT) to certain degree?

edit I have tried going past 296 at lower multi ie 10/9x using RMclock but it doesn't go further

 

That's what it looks like. I wouldn't push it. If the GPU is showing artifacts, you're treading on thin ice. I've hosed components before doing that Learn from my mistakes.

 

When I overclock its just the FSB. The PCI E remains where it is so the GPU is perfectly stable in fact I can even OC it with the CPU at 3.25ghz. Artifacts are just when I up the PCI E separately. I intend not to touch the PCI E again was just checking with all the experts here as to what could be limiting my stable OC(3.25) where I use the normal PCI E frequency. Your concern is appreciated however

 

How are you doing this overclocking? Do tell because if i can do it i would like to try it.

 

I personally use Clockgen to carry out the OC but SetFSB works too. Simply select the correct PLL ( for me CY25881 ). It differs from chipset to chipset I believe, then overclocking is possible.