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Nvidia GTX 780 running at PCIe 2.0 4X speed only..

Tags:
  • Gtx
  • Graphics
  • Speed
  • Nvidia
Last response: in Graphics & Displays
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May 21, 2014 2:06:11 PM

Can anyone shed some light as to why my Nvidia GTX 780 is running only at 4x speed?

I have an Asrock Z68 Professional Gen3 with an intel 1155 I7 Sandy Bridge 2600K processor.

Here is the kicker..this motherboard will not support the video card running in the top lane whatsoever (which I know is where I need to have the video card for the 16x speed to register and run.) I have been having trouble with this for 3 years and after recently upgrading my GPU to the 780 gtx I am ready to get this lined out.

I ended up purchasing a Asus Sabertooth z87 motherboard to see if maybe it was the Asrock pcie lanes that were faulty. However, after installing the Asus z87 board I couldn't get ANY image to display from the GPU at all.

I have tried nearly every idea I can possibly think of..I know the GPU isn't at fault because I have in it the bottom slot in the Asrock z68 lane right now and I can see and function. My only thoughts are something with my processor must be the culprit? I don't know..I kind of can't gather my thoughts as to what measures I need to take to get this lined out. I hope someone here can maybe shed some light on the issue for me..Thank you in advance!

More about : nvidia gtx 780 running pcie speed

a b Î Nvidia
May 21, 2014 2:08:58 PM

What model PSU do you have? Admittedly I don't think it's related, but it would be nice to be able to rule it out completely.
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May 21, 2014 2:09:43 PM

If it runs at 2.0 4x you won't really see a difference to 3.0 16x. Maximum 0.1 FPS more.
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a c 94 Î Nvidia
May 21, 2014 2:11:02 PM

Did you reinstall windows after changing mother boards ?
Did you uninstall GFX drivers before switching cards ?

And yes, all my PCI-E 2.0 builds were 16X (single / SLI) whereas all the PCI-E 3.0 builds have pretty much been 16x single and 8x (SLI) ....x4 on PCIE-2.0 musta been annoying.

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May 21, 2014 2:16:19 PM

What processor are you using on the Z87 board? Your 2600K won't work on it.

Casey
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May 21, 2014 2:28:16 PM

I have an 850w Psu, I have done a fresh install of windows 7 64 bit. Whoops, I'm sorry about the mistype, i actually have the z77 sabertooth mobo. I have not changed my processor yet, it's still the sandy birdge 2600k.

So, even though my computer is running my gtx 780 at PCIe 2.0 4x speed I really am not taking a performance hit?

and thank you all for such quick responses!

**Here is a screenshot of the information from CPU-Z and GPU-Z

**
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a c 94 Î Nvidia
May 21, 2014 2:41:57 PM

Ivy Bridge provides PCI-E 3.0 support. I remember reading that PCI-E 3.0 x 8 is roughly equivalent to PCI-E 2.0 x16

Most of the articles on the subject address what happens in SLI or CF where adding the 2nd card drops the slot to x4..... example:

http://www.tomshardware.com/reviews/crossfire-meets-pci...

Quote:
Better not use the third slot for current graphics cards - it only has x4 PCIe lanes.



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May 21, 2014 2:46:02 PM

No as i said a maximum oft 0.1 fps at all
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May 21, 2014 2:47:48 PM

Do you have any other PCI Express cards installed? Some motherboards will reallocate PCI Express lanes from the graphics card(s) to other slots.

If you have a graphics-intensive program running at the same time as GPU-Z, does the bus interface change? The question mark next to the bus interface box in GPU-Z should open a screen to load the card.

Casey
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May 21, 2014 3:33:28 PM

Only the GPU is in a pcie slot. What's strange is, no matter what I do, I cannot get the GPU to send a signal in the primary GPU slot. The only way I get video is if I put it in the last Pcie slot on this Asrock Mobo. If I put it in the Asus Sabertooth I can't get any signal other than from the onboard video. Even when I got into the BIOS and force it to the PCIE lane for VGA. But if I drop this GTX 780 in an old Nvidia 790 motherboard that I have it picks it up flawlessly. Needless to say, it's aggravating that I can't use this GPU in my "primary" pcie slot. Obviously it's working for me in the last 4x slot on this motherboard, but I do wish it would work properly on my Asus sabertooth. I have gone to some extreme lengths to get this figured out. I also purchased a Gigabyte z68 mobo back when I thought the Asrock was defective. Same exact issue..it's like nothing I try to do, reformatting hard drive with fresh windows 7 installation and drivers and motherboard flash updates for the bios..all of that. But it always leads me back to this. So for the time being I have my GPU in the bottom 4x slot on my asrock z68 mobo. As that is the only setup I have found to allow me to function and utilize this card. I am surprised however, that running this card with Pcie 2.0 at 4x speeds isn't that much different than lets say the 16x speed. I did find out that this particular sandy bridge CPU does not support PCIE 3.0 speeds. I have thought about completely upgrading my CPU and Motherboard entirely (My machine is mainly used for music production, but on the side I play games here and there.) However, being the type of person that I am, I just wish I could figure out what the exact problem is that is causing this particular issue.

Yes, I have ran the GPU-Z render test to see if the PCIE lanes would change from 4x speed to 8x or even 16x, but to my luck it stays at 4x speed.

Does it make sense at all that if the GPU is in the top 16x lane it doesn't register the GPU being installed at all. As well as the 8x lane, but if it's in the 4x lane it registers the GPU and I can use it as my primary GPU instead of the CPU built in onboard graphics card?
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Best solution

a c 94 Î Nvidia
May 21, 2014 3:54:40 PM

Found another source .....

http://www.tested.com/tech/457440-theoretical-vs-actual...

Quote:
Everything down to x16 1.1 and its equivalents (x8 2.0, x4 3.0) provides sufficient gaming performance even with the latest graphics hardware, losing only 5% average in worst-case.....

The most interesting part in these results is the finding that last year's most powerful graphics cards perform just fine at PCIe 2.0 x8 or even PCIe 3.0 x4.


So from PCI-E2.0 x16 to x8, you are looking at a 5% worse case performance loss. Based upon the graph here....it would seem you were losing 13% of your performance at PCI-E 2.0 x4 w/ ya Sandy Bridge setup



PCI-E 2.0 x16 = 100%
PCI-E 2.0 x4 = 87%

In short, w/ Sandy bridge setup, you were getting GTX 770 like performance out of your 780. (115% x 87% = 100%) so I can certainly understand your frustration getting the performance of a card that is $180 cheaper than the card you bought.



It gets better w/ Ivy bridge.

PCI-E 3.0 x16 = 101%
PCI-E 3.0 x4 = 96%
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May 21, 2014 4:11:00 PM

Thank you very much for the info and going through the trouble to shed light on all of this. This is very appreciated Jack! As well from everyone else that has been helping me out here! Well, I suppose I am just trying to figure out what my next step should be. I would really like to simply resolve the issue of the other pcie lanes on my motherboard. I just can't understand why my GTX 780 will not be recognize in the upper lane. I know the lane isn't completely faulty because if I slap in an older GPU such as my nvidia 550 ti or 260 gtx or even my old nividia 9800 GT they work fine in the upper slot and run. Only my GTX 780 will not register. The fans run and everything but I get no signal. I have typically connected the onboard via HDMI just so I can go to the desktop and see what the Device manager says for my GPU but it never registers it. That, or the 8x lane. Only the 4x lane :( 
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a c 94 Î Nvidia
May 21, 2014 4:21:32 PM

What brand is the GFX card .... I'm hoping you say Asus as you can put it in the Sabertooth and keep them on the phone till it's fixed. had that battle w/ EVGA as their card wouldn't run at advertised speeds and I had to down clock to keep stable. They blamed 850 watt PSU (10.0 jonnyguru performance rated, they blamed memory (Mushkin Redline), they blamed MoBo (Rampage III) ..... but had no answer as to why running two Asus cards in SLI had no issues with a 25% overclock and yet their card could not run at it's advertised factory OC. This went on thru 20 support calls over 18 months including numerous replacements. After 4 RMAs they finally shipped a next generation card (reference, not factory overclocked) that worked.

First lesson taught in Tech Support 101.... "Blame another component manufacturer and get the dude off the phone ! "
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May 21, 2014 4:37:52 PM

wow...that sounds like a complete nightmare! Sadly..I believe my Nvidia 780 GTX is in fact an EVGA..Let me check the box right quick (I can't remember off the top of my head.)

**it is in fact and EVGA card**

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a c 94 Î Nvidia
May 21, 2014 5:09:41 PM

Well all I can say is document everything an be insistent. You will be told it's the MoBos fault .... so make sure to tell them you have had it in 3 motherboards.
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May 21, 2014 6:19:04 PM

Thanks again Jack, I will definitely do that. As soon as I get this situation resolved in whatever manner it may be, I'll post back and let everyone know what I ended up doing as the final solution. Thanks again!
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a c 94 Î Nvidia
May 21, 2014 7:24:03 PM

Muchos Grassyass
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