Asus Strix Z270 x16 PCI-E slot slow - Anyone know why?

Man1ac

Man1ac

Man1ac

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9 Aug 2017
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Hello all,

I have put together a micro ATX build that consists of the following:

Asus Strix Z270G Mini ITX
16Gb 2400 Mhz GSkill RAM
Samsung 951 M.2 installed on front M.2 socket
Corsair H100i AIO rad
Intel 6700k processor
Corsair 760 Watt PSU
MSI 1080 Armor GPU

Now, here's the problem, when the graphics card is in the 1st PCI slot on the motherboard, the graphics capabilities are drastically reduced (getting 24 FPS max in everything but Unigine where that reports 60 - 70 fps. (probably because it's a synthetic benchmark)

However, when i move the card down to the 2nd pci-e slot, the games run perfectly, and at 100+ fps.

I have turned off VSync and turned down all the graphic niceties, I just cannot get any games running at an acceptable rate on the 1st PCI bus.

Has anyone else experienced this? and is this a simple fix, or is an RMA in order?

My concern . now, is that i am stifled if I buy a second GPU to compliment the first, the first PCI bus connector is going to drag the second one down to it's speed.

The second concern, looking at the manual, is the 2nd PCI connector is operating at x8 speed, so am I also not seeing the x16 benefit.

I have tried everything I can think of, the card is operating at 45 degrees, so it doesn't appear to be thermal throttling.

Can anyone shed any light on what else i can try here please?

I am pulling what little hair I have left out in trying to figure out what is happening here.

Thanks a lot.
 
Have you checked how many PCI-E lanes the the graphics card is using when it's in the first slot? BIOS on that board should tell you - it does on my Asus Z270I - but you can also check it out in Windows with something like GPU-Z too. If it isn't reporting as X16 for that slot then it could be worth reseating the CPU and/or loosening the screws for the H100i a tad.

My reasoning here is that I have heard of CPUs/motherboards not registering the correct amount of RAM installed when the heatsink mounting has been done up too tightly. This has somehow been caused by the excessive pressure which in turn causes some of the CPU socket pins to not make proper contact with the CPU - perhaps it could be something like that happening here but with pins controlling that PCI-E slot. A long shot, admittedly but worth looking at.

Also, since it's a new build I assume it's a clean install of Windows?
 
Phemo,

Having built around 15 PC's in the last 25 years, I am no stranger to the inside of a machine (i wish i could say the same about my cars)

I did as you suggested, and loosened what seemed like not too tight pump screws from my motherboard (1 screw did seem tighter than the others)

to my surprise, the graphics card was placed in the top pci-e slot, the computer was turned on, and it's all working fantastically now. :)

So, Kudos where it's due, you hit the nail on the head, well done and thank you.

You are also right, Windows 10 was installed for this build as a fresh install.

As this was also a build for a friend, he'll be a very happy person.

And me, roll on the release/stock gain of the Rampage VI Extreme, which I will be putting together once I have the board in my hot hands.. lol

Thanks again,

M.
 
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