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Z170 Extreme4+ U.2 and GPU Conflict

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Category: Technical Support
Forum Name: Intel Motherboards
Forum Description: Question about ASRock Intel Motherboards
Printed Date: 08 Dec 2023 at 1:36pm
Software Version: Web Wiz Forums 12.04 -

Topic: Z170 Extreme4+ U.2 and GPU Conflict
Posted By: sfec-eric
Subject: Z170 Extreme4+ U.2 and GPU Conflict
Date Posted: 28 Aug 2015 at 10:50pm
Hello all,

First off, I'd like to introduce myself to the forum.  There's some great information here!  I've been a fan of ASRock for quite a while.  Between my home gaming rigs, builds for friends and family, and builds for my office, I have assembled around 25 ASRock based computers in the last few years.

Now, on to my issue.  I'm putting together my new build at the moment.  I opted for the Z170 Extreme4+ as it had support for NVMe via M.2 and the ASROCK U.2 kit.  I purchased an Intel 750 with the SFF-8643 connector so I didn't block airflow / PCIe slot / get with the times / etc.  However, I seem to have a conflict with the U.2 kit and my GTX 780 (will be upgrading to Pascal when it comes out).  I physically cannot lock my GPU into the slot as the U.2 kit is in the way.

Are there any known solutions to this?

After a few drinks, I was just going to bend / cut some heatsink blades off my video card, but then realized that probably wasn't the best solution.  So I slept on it.

My first (sober) thought was to mount my GPU in the 2nd x16 slot, although this slot only runs at x8 electrically.  I would hate to throttle down my GPU because of this, plus this will limit my SLI abilities in the future.

My second thought was to find a flexible M.2 extension cable similar to this: so I can physically mount the kit in a different location, although that may limit my bandwidth.  Ideally, I'd like to bypass the kit and find a cable that goes from M.2 to mini SAS HD, if that exists yet, or is even possible.

Should I return the SFF-8643 connected drive and the U.2 kit and go with the PCIe version?  If so, will having this card plugged into PCIE6 (x16 mechanical, x4 electrical) force PCIE2 to run at x8, thereby still cutting my GPU's bandwidth in half?

Thanks in advance!

Posted By: Xaltar
Date Posted: 29 Aug 2015 at 12:58am
The Skylake platform supports 36 PCIE lanes total, 16 from the CPU and 20 from the PCH so no, it shouldn't force PCIE2 to x8. Personally, I would go with the trade in for the PCIE version as it will likely be the most practical solution that won't void any warranties or bottleneck the 750 or GTX 780. 

Running the 780 in x8 mode will not bottleneck it as it is not able to saturate the PCIE 3.0 x8 bandwidth anyway. If you would rather keep the U.2 kit then you should be fine with that route. As for SLI options later, you may need to make another plan then.

Welcome to the forums Smile

Posted By: sfec-eric
Date Posted: 29 Aug 2015 at 2:31am

Thank you for the quick reply!

With returning the U.2 drive and buying the PCIe version instead, I'm at about the same cost as just returning the Extreme4+ and going with the Extreme7+ instead.

That, coupled with me wanting to go SLI in the future may have just made this decision a lot easier.  I see there are more M.2 slots on the Extreme7+, and the first one shouldn't interfere with my GPU.  Win-win?

Posted By: Xaltar
Date Posted: 29 Aug 2015 at 2:36am
I didn't want to suggest it because I was not sure about your budget lol

The extreme 7 would be my choice for sure.

Posted By: sfec-eric
Date Posted: 29 Aug 2015 at 2:46am
Newegg had an open box discount on one.  I've usually had pretty good luck with them.  I'm in no rush on this build, still waiting on the 6700k to be available.  Hopefully I won't be waiting too long.

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