Asrock x79 Extreme4 & GTX 780: PCIe 3.0 issue again

magellan · Apr 24, 2014

I couldn't find the old thread I had dealing w/this issue, but I have more information
now.

When I have the PCIe slots set to Gen3 in the BIOS, I can't boot the system w/my old ATI 6970 (yep it was still ATI when I bought it). If I switch the PCIe slots to Gen2, the system boots. So, it looks to me like the motherboard and CPU (i7 3820) are capable of running at PCIe 3.0.

Does anyone know how I can get Windows 7 or Windows XP Pro to run the PCIe slots in 3.0? I tried the Nvidia patch (which was written to force GTX 6xx series GPU's to use PCIe 3.0 mode) but it didn't make any difference (I tested w/GPUz and used their special utility to put a load on the GPU), the slot still stayed in PCIe 2.0 x16 mode at most (if I close the GPUz utility that loads the GPU it reverts from PCIe 2.0 to PCIe 1.1).

Maybe there's a registry setting I can change to force PCIe 3.0 mode -- kinda like the old nvidia coolbits tweak?

ATMINSIDE · Apr 24, 2014

Is the 1% that you'll gain really worth all the hassle?

magellan · Apr 24, 2014

Why not get that extra 1%? For some games the difference is more significant (i.e. Alan Wake).

According to Intel's official spec sheet, the i7-3820 doesn't support PCIe 2.0:
http://ark.intel.com/products/63698/Intel-Core-i7-3820-Processor-10M-Cache-up-to-3_80-GHz

If I was running an IvyBridge-E would Nvidia allow PCIe 3.0 then?

ATMINSIDE · Apr 24, 2014

I'm going to pull this from your other thread:

ATMINSIDE said:
IIRC Sandy Bridge doesn't support PCIe 3.0, only Ivy Bridge.

That post was directed toward both SB and SB-E.

But yes, IB-E should allow PCIe 3.0, because that's when Intel started supporting PCIe 3.0.

wingman99 · Apr 25, 2014

Sandy Bridge E & X79 PCIe 3.0: It Works
http://www.anandtech.com/show/5264/sandy-bridge-e-x79-pcie-30-it-works

QUOTE:Simply enabling PCIe 3.0 on our EVGA X79 SLI motherboard (EVGA provided us with a BIOS that allowed us to toggle PCIe 3.0 mode on/off) resulted in a 9% increase in performance on the Radeon HD 7970. This tells us two things: 1) You can indeed get PCIe 3.0 working on SNB-E/X79, at least with a Radeon HD 7970, and 2) PCIe 3.0 will likely be useful for GPU compute applications, although not so much for gaming anytime soon.

ATMINSIDE · Apr 25, 2014

PCIe Gaming Performance.

Recall that PCIe 3.0 x8 = PCIe 2.0 x16

Like wingman said (which is consistent with my 1% number from earlier), not worth it for gaming.

Woomack · Apr 25, 2014

I've noticed that some older gfx cards are simply not working on some new boards with pcie 3.0. You have to boot with some other card and switch it manually to 2.0 or use 2nd pcie slot. However I had only issues with older cards than AMD 6 series.
About the same I had on X79 and Z87 boards but using 2.0 slot is not causing performance drop for anything pre AMD 7900 series.
Software is usually reading pcie mode wrong and correct readings are almost always in 3D/high load. That's why in GPU-Z to check pcie on some new cards, you have to use full screen 3D test.

magellan · Apr 26, 2014

It's kinda annoying that I have a motherboard that advertises PCIe 3.0, a video card that advertises PCIe 3.0, but I can't do PCIe 3.0.

EarthDog · Apr 26, 2014

Again, I don't not recall your cpu supporting pcie3 without some 'hack'???

ATMINSIDE · Apr 26, 2014

magellan said:
It's kinda annoying that I have a motherboard that advertises PCIe 3.0, a video card that advertises PCIe 3.0, but I can't do PCIe 3.0.

Because your PROCESSOR doesn't advertise PCIe 3.0...........

magellan · Apr 26, 2014

ATMINSIDE said:
Because your PROCESSOR doesn't advertise PCIe 3.0...........

There's nothing on the motherboard box that states it only supports PCIe 3.0 if an Ivybridge-E CPU is installed, but it is in the motherboard manual so OBVIOUSLY they know about it.

Alternatively, why doesn't the video card manufacturer put such a warning on the website or on the video card box? After all, it's not like Nvidia doesn't know about it.

ATMINSIDE · Apr 26, 2014

magellan said:
There's nothing on the motherboard box that states it only supports PCIe 3.0 if an Ivybridge-E CPU is installed, but it is in the motherboard manual so OBVIOUSLY they know about it.

Because that would be bad marketing.
Intel lists PCI Express Revision as 2.0 for the i7-3820. That's all the warning you need, as the company that has the product directly responsible for it not being supported has it listed clearly.

Alternatively, why doesn't the video card manufacturer put such a warning on the website or on the video card box? After all, it's not like Nvidia doesn't know about it.

Because it isn't their product that isn't supporting PCIe 3.0...

RGone · Apr 28, 2014

http://ark.intel.com/products/63698/Intel-Core-i7-3820-Processor-10M-Cache-up-to-3_80-GHz
Intel® Core™ i7-3820 Processor
(10M Cache, up to 3.80 GHz)

SPECIFICATIONS
Expansion Options
PCI Express Revision 2.0
Max # of PCI Express Lanes 40

magellan · Apr 30, 2014

What about the various LGA 2011 Xeons? Do they have PCIe 3.0 capabilities?

EarthDog · Apr 30, 2014

Not sure off the top of my head for SB-E based Xeon's, though, I don't believe so. It was IB-E that brought in that support IIRC.

If you google the part, it should return an intel white paper link which you can then find that information out (see RGone's link directly above your last post).

ATMINSIDE · Apr 30, 2014

magellan said:
What about the various LGA 2011 Xeons? Do they have PCIe 3.0 capabilities?

Its listed on Intel's spec page for each individual processor.

Asrock x79 Extreme4 & GTX 780: PCIe 3.0 issue again

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