X99 Gmaing i7 / 6800k
Printed From: ASRock.com
Category: Technical Support
Forum Name: Intel Motherboards
Forum Description: Question about ASRock Intel Motherboards
URL: https://forum.asrock.com/forum_posts.asp?TID=3594
Printed Date: 20 Jul 2025 at 11:17pm
Software Version: Web Wiz Forums 12.04 - http://www.webwizforums.com
Topic: X99 Gmaing i7 / 6800k
Posted By: Go18Go
Subject: X99 Gmaing i7 / 6800k
Date Posted: 15 Oct 2016 at 10:32pm
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I was hoping someone could tell me what im missing on my setup here. I can not get PCI-e width to 16x with 1080gtx sli. I just upgraded from a Asus x99 deluxe with 5820 and 980 gtx in sli and had 16x width. I changed tot he new setup mostly to get m.2 and i have a bootable 950 pro. the system works perfect just cant figure out the width reduction. And it does not change under load, always stays at 8x I know ultimately it doesn't matter but it does matter from a phsyc standpoint when you build a whole new system and go backwards on paper, you know what i mean? Especially when i think its jkust a simple setting somewhere im missing. Any ideas would be appreaciaioted
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Replies:
Posted By: parsec
Date Posted: 15 Oct 2016 at 11:28pm
Which PCIe slot are you using for the video card? That can make a difference with your CPU that has 28 PCIe lanes. From the specs for your board: If you install CPU with 28 lanes, PCIE2/PCIE4/PCIE5 will run at x16/x0/x8 or x8/x8/x8 You can try clearing the UEFI/BIOS (save your settings in a profile first) and then check the width again. That normally will fix that issue, if the video card is in the appropriate PCIe slot. ------------- http://valid.x86.fr/48rujh" rel="nofollow"> 
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Go18Go wrote:Posted By: Xaltar
Date Posted: 16 Oct 2016 at 12:35am
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You mentioned GTX 1080 SLI, I take it you have 2 GTX 1080s? As Parsec noted, make sure you are using the correct slot config. ------------- 
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Posted By: Go18Go
Date Posted: 16 Oct 2016 at 8:02am
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The cards are in 2 and 4. I have no sata drives connected to affect lane speed, and only have a single m.2. |
Posted By: parsec
Date Posted: 16 Oct 2016 at 10:34am
Thanks Xaltar, I missed the SLI configuration!  That explains it, plus you are using an i7-5820K, and an M.2 SSD, in the M2_2 slot. Your i7-5820K has 28 PCIe 3.0 lanes, not 40 that the higher priced models do. So... First, dual SLI of x16 + x16 = 32 lanes, impossible with your CPU. From specifications, which I included in my previous post: If you install CPU with 28 lanes, PCIE2/PCIE4/PCIE5 will run at x16/x0/x8 or x8/x8/x8 When you put a video card in the PCIE4 slot, with your CPU, then all three slots will run at x8. That is why both cards run at x8. The best you can do is run one card in PCIE2 at x16, and the other card in PCIE5 at x8. I'm guessing your PC case won't allow you to use a dual slot card in the PCIE5 slot? Using the M2_2 slot for a PCIe SSD that is configured as PCIe 3.0 x4. The M2_2 slot uses four of the PCIe 3.0 lanes from the CPU. That is how all X99 boards are with M.2 slots that are PCIe 3.0. This makes no difference with a 28 PCIe 3.0 lane CPU. There is no way you ran both 1080's at PCIe 3.0 x16 on the Asus board with an i7-5820K. The main limitation here is the i7-5820K, and its 28 PCIe 3.0 lanes. The specs and math all add up, there's no setting that can change that, sorry to say. ------------- http://valid.x86.fr/48rujh" rel="nofollow">
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Posted By: Go18Go
Date Posted: 16 Oct 2016 at 11:58pm
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That's exactly right. Thanks for pointing me in the right direction. I was stuck on the fact that i had a 4820 and got 16x, When i look up the specs for 4820 it does have 40 lanes wheres as my 6800 has 28. I also ran just one card in slot 2 and got 16x. I guess i should have gotten the 6850 or 6900 Thanks for the help guys
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Posted By: J Z
Date Posted: 17 Oct 2016 at 12:24am
i7-5820K also has only 28 lanes. i7-5930K has 40 lanes  Edit: Sorry, i7-4820K has 40 lanes. ------------- Kind Regards, JZ https://shop.JZelectronic.de - Der Shop mit ausgesuchter ASRock Profi Hardware https://www.facebook.com/asrock.de |
Posted By: Xaltar
Date Posted: 17 Oct 2016 at 12:35am
It wouldn't really give you any performance improvement (regarding the extra PCIe lanes obviously). I have yet to see a GPU that can fully saturate the bandwidth of PCIe 3.0 x8. I see where you are coming from though, it bugs the hell out of me when I see something on my system is not operating at it's full potential  -------------
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