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PCI-E 3.0 stuck at x4 Speeds

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  • CPUs
  • Motherboards
  • PCI Express
Last response: in Motherboards
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May 24, 2013 3:41:31 PM

So I recently purchased a new motherboard and CPU, in the manual it says that the motherboard has 2 PCI-E x16 (pci 3.0 when running with Ivy Bridge CPU which is what I have) slot but when in dual mode it runs at x8/x8.

My PCI-E 2 is running at x4 speeds and my PCI-E 3 is running at x8. How can I change the x4 speed up to x8 like it says in the manual.

System Specs:
CPU: i7 3770k @Stock speeds (3.5ghz)
Mobo: ASRock z77 Extreme 4 (Running the latest Bios)
RAM: 16GB Corsair Vengeance (XMP profile)
Graphics: 2GB XFX 6950 PCI-E 2.1 & 1GB XFX 6950 PCI-E 2.1 (with crossfire bridge)
PSU: Corsair GS800 (800W)

I have looked in the Bios to see if there is a setting I could change to get x8 speeds, I changed the bus lanes to PCI-E 2.0 from 3.0 and still no change in the x4 speed. I also upgraded to the latest Bios from P2.50 to P2.80. I have taken a card out from PCI-E 3 and ran only one lane and still only getting x4 speeds.

I have tested my cards on metro 2033 and have gotten some crazy results.
First I was just checking out what I would get in crossfire on max settings with PhysX turned off I was getting about 30 FPS which is a massive drop from to what I was getting on my old build. I though it must be the 1GB card bottlenecking the 2GB card. So i decided to check what the performance would be like when i disable crossfire and i was hitting between 60-80 FPS. Now I decided to check out the performance with PhysX turned on and boom straight back down to 30 FPS. disabled it again and FPS stayed down at 30. I am not sure if its the PCI-E lane not waking up from a power saving state as I once had a burst of frames in one of my tests ( at this time i didn't check my PCI-E's lane speed and I am unable to replicate the results.

When one card it plugged into the PCI-E 2 it runs at x4 speeds and whenI crossfire It stays at x4 and x8. What gives its suppose to be x8/x8. I have seen similar problems that people have run into with this board where they are stuck at running x8 speeds and not x16 on a single slot.

I have also tried this with an i7 3770 and got the same results and my 3770k

A friend of mine also purchased the same motherboard and is running it with i5 3570k @4.5GHz with one card plugged into the PCI-E and he is getting PCI-E 3.0 x16 speeds.

Just for some background on my old build and the performance I used to see.
AMD 8150
MSI 990FXA-GD80
same graphics cards and ram

On Metro 2033 I would be putting over 60 FPS on maxed settings with PhysX turned off.

More about : pci stuck speeds

a c 114 à CPUs
a c 559 V Motherboard
May 25, 2013 2:13:08 AM

Hi, It might be a bent pins issue. Try reseating the CPU and checking the socket for bent pins.
If no bent pins, an option would be RMA-ing the board.
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May 25, 2013 2:43:39 PM

alexoiu said:
Hi, It might be a bent pins issue. Try reseating the CPU and checking the socket for bent pins.
If no bent pins, an option would be RMA-ing the board.


Ok i will try this tomorrow and report back, although i don't think this is the case as the same thing has happened with a different CPU.

I have also send an email to ASRock and still waiting for a reply.
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a b V Motherboard
May 25, 2013 9:29:23 PM

The video cards - one card is 2gb and the other is 1gb, that might factor into something.
The 2 x PCIe slots are 3.0 interface, your video cards are only 2.1 interface.

The information is rather vague -
"2 x PCI Express 3.0 x16 slots (PCIE2/PCIE3: single at x16 (PCIE2) / x8 (PCIE3) or dual at x8/x8 mode)"
My mind makes me think that you need to use slots PCIe 2 & 3 to acquire the x8 for both cards.
http://www.asrock.com/mb/Intel/Z77%20Extreme4/?cat=Spec...
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a b à CPUs
a c 210 V Motherboard
May 25, 2013 10:46:11 PM

It wouldn't hurt if the graphics cards were identical. You'd be flying high if they were. Pop two identical cards into those two PCIE 3.0 slots and it should work like a champ. Or one card into the first PCIE slot would get you better results too. And set them back to 3.0 in BIOS. The 3.0 slot will handle 3.0 and lower cards too that fit into the slot.
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May 26, 2013 3:54:49 PM

TenPc said:
The video cards - one card is 2gb and the other is 1gb, that might factor into something.
The 2 x PCIe slots are 3.0 interface, your video cards are only 2.1 interface.

The information is rather vague -
"2 x PCI Express 3.0 x16 slots (PCIE2/PCIE3: single at x16 (PCIE2) / x8 (PCIE3) or dual at x8/x8 mode)"
My mind makes me think that you need to use slots PCIe 2 & 3 to acquire the x8 for both cards.
http://www.asrock.com/mb/Intel/Z77%20Extreme4/?cat=Spec...


Yes I am using both slots for my graphics cards and i am getting x4/x8 speeds when I should be getting x8/x8. And like i mentioned with my old PC build on my MSI board they did both run at x16/x16 speeds and my framerate on games like metro was over double

spooky2th said:
It wouldn't hurt if the graphics cards were identical. You'd be flying high if they were. Pop two identical cards into those two PCIE 3.0 slots and it should work like a champ. Or one card into the first PCIE slot would get you better results too. And set them back to 3.0 in BIOS. The 3.0 slot will handle 3.0 and lower cards too that fit into the slot.


I have change my Bios setting to Gen 3. Gen 2. Gen 1 and set to Auto and it still runs at x4 Speeds with any of the 1 cards in the top PCI-E 2 slot.

Also i checked for bent pins on my CPU and its fine, I also tried with a completely different processor
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a b V Motherboard
May 26, 2013 4:37:29 PM

If you are only using one of the video cards for video out, you don't need the crossfire bridge.

Edit - If you are using a cable out from each of the video cards (to two different monitors) then try a different cable in a different port.
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a b à CPUs
a c 210 V Motherboard
May 26, 2013 7:49:01 PM

See if there is an updated video driver for the graphics cards?
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May 27, 2013 10:56:39 AM

TenPc said:
If you are only using one of the video cards for video out, you don't need the crossfire bridge.

Edit - If you are using a cable out from each of the video cards (to two different monitors) then try a different cable in a different port.



No I'm not using a crossfire bridge when only testing 1 card for each slot. Why would I need a crossfire bridge when there is only one card in the slots? but when i do use dual cards I am using the crossfire bridge.

spooky2th said:
See if there is an updated video driver for the graphics cards?


Already done this and everything is up to date.

Come to the conclusion that the lanes are faulty and I'm returning it and buying an MSI board

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a c 114 à CPUs
a c 559 V Motherboard
May 27, 2013 11:31:16 AM

Just out of curiosity, after removing the CPU, check the CPU socket and see if there are bent pins.
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May 27, 2013 11:34:23 AM

alexoiu said:
Just out of curiosity, after removing the CPU, check the CPU socket and see if there are bent pins.


Ye I have done and it looks fine. I also tried a completely different CPU and the same thing happens.
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a b V Motherboard
May 29, 2013 12:29:45 AM

16GB Corsair Vengeance (XMP profile)

It could be your ram, the QVL suggest 1.65v ram but I think your ram is only 1.5v
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