Help! My slow PCIe is slow - Maximus VI GENE

[UncleJoe]

Hi. I got a Maximus VI GENE yesterday. One of the first tests I did was run the GPU bandwidth test (from CUDA SDK), but I only get a disappointing ~3 GiB/s. This was the same speed I was getting with my previous PCIe 2.0 motherboard and GTX 680 in x8 mode.

I looked in the BIOS under the N.B. PCI express configuration and noticed it said x4 for 1 port and empty for another port. If it was really operating in x4, then that would explain the sluggishness (4 x 8 Gbit/s = 4 GB/s). I also tried setting the link speed from auto to gen3, but that didn't help.

I have the following plugged in:

1. GTX 680 in x16 slot
2. RevoDrive 1 in x4 slot
3. Intel 6200 Wifi/Bluetooth in MPCIe slot

Please help !

[HiVizMan]

UncleJoe wrote:
"Would you please clear CMOS and boot into OS again"
I did "load optimized defaults" and it didn't help, and I only have one PCIe 3 device (GTX 680), and 2 PCIe 2 devices

I tried unplugging the RevoDrive, but the GTX 680 still remains in x4 mode.


In my case, no because I plugged it into the x4 slot which is PCIe 2.0 only. And even if it shared, it should be split as x8 not x4

You have something plugged into the very bottom PCie slot?

Please if possible try with nothing in your PCIe slots but the graphic card.

[UncleJoe]

The manual is here and there is a downloads page on the ASUS web site
http://dlcdnet.asus.com/pub/ASUS/mb/LGA1150/MAXIMUS-VI-GENE/E8182_Maximus_VI_Gene.pdf

Please if possible try with nothing in your PCIe slots but the graphic card

I've already removed the Revodrive, so there would be nothing in any of the 3, PCIe 3.0 slots (except the GTX680), leaving only the PCIe 2.0 slots. And I really don't think the PCIe 2.0 slots will share bandwidth with the PCIe 3.0 slots because they're physically separate connections:


"Please if possible try with nothing in your PCIe slots but the graphic card"
I think I'll save that for later. I don't want to deal with with lost screws and scrapped fingers trying to tear down a small form system - I have a Silverstone SG03.

Hey, look, I really appreciate the help I'm getting, but I'm not in that much of a rush. I've already filed this problem to ASUS tech support. Let me wait and hear back. If they say my setup should work in x16, then maybe something is wrong with the GTX680, so I can try that in another computer and try another board in this computer.

[Menthol]

ASUS has made some very nice boards for Haswell, but Haswell has it's limitations and there could be some disappointment if you don't do your research and purchase the model that suits your needs.

[Menthol]

It is weird this model is not on the ASUS website so I cannot find the manual, In the advanced settings of the bios somewhere there is pcie lane control - auto or you can over ride and set lane speed, this may at least let you know what options you have, also you my want to try disabling your on chip GPU, you re correct that it should at least give you 8x8. The only reference I have is my MVIE which has a plx chip so I will have completely different options.

[HiVizMan]

All good mate - it is your call after all. But do post back with what you find out or if you find the fix.

Enjoy your system.

[UncleJoe]

Alright, I've gotten a big clue. When I plug in a GTX 480, it runs fine in x16 mode *and* with my RevoDrive and Wifi card plugged in together. But the GTX 480 is only PCIe 2.0. Out of curiosity I tried lowering the link speed to 2.0 with my GTX 680 to see if that helps, but it didn't.

So it seems the problem has been narrowed down to either the graphics card or the motherboard. What should I do next?

[Pratham]

UncleJoe wrote:
What should I do next?

Try your GTX 680 in another system obviously...If you don't find maximus vi gene then find maximus vi hero or something similar. one more question Have you tried updating your BIOS? I don't know how will that help though..

[Menthol]

I swapped out the 7970 and replaced with a GTX 680 on the M6E with default settings in the bios and only XMP for my 2666 RAM, it is detected and runs at PCIE 3.0 X 16



Another story is the 7970 Matrix on my RIVE bios is full screen not the small screen as on the MVIE??? anyone. difference is motherboard and monitor ASUS 27" 1080p on the MVIE and Dell 30" 2560x1600 on RIVE

[UncleJoe]

Problem found. It's almost certain that the MSI GTX 680 is at fault. Here's what I found:

1. GTX 680 in Maximus VI - runs at 4x PCIe 3.0
2. GTX 480 in Maximus VI - runs at 16x PCIe 2.0
3. GTX 680 in Dell Precision T5500 - runs at 8x PCIe 2.0 (even 4x PCIe 2.0 if tried in another x16 slot)
4. GTX 560Ti in Dell Precision T5500 - runs at 16x PCIe 2.0

I don't want to RMA yet if there's something obvious and easy I can repair on the board. Is there?
Graphics wise, I'm not too concerned since I've been running BF3 with graphics maxed out and with smooth performance for a year. I'm just concerned that there might be some bandwidth hungry CUDA application I want to do some day that needs x16. Maybe even that is moot if Maxwell is coming out next year.

[UncleJoe]

Well, I finally found the problem.


Note: the picture isn't from my bad GTX 680.

I chipped a surface mount component near the card edge (most likely a high pass capacitors used by a PCIe data lane). I found this by using a multimeter to probe each the data links and found something strange with one link.
It seems once a lane is bad, none of the lanes above it can be used either, therefore making the card stuck in 4x.

Guess I'd better be more careful in the future when inserting cards in a small chassis.

Has anyone else encountered this or has even attempted to replace the capacitor !