PCI and SLI: What are the most optimal lane choices (x8/x8 vs. x16/x4)?

[christopherhammond87]

Hi all!

First time builder here. I have a MSI MPower Titanium Z170 motherboard and 2 EVGA 1080 SC's, and wanted your input on the best way to place them.

My motherboard has 3 PCI lanes for graphics cards, and from top to bottom they are x16, x8, and x4. The recommended setup is to use the top 2, with the computer running in x8/x8, while this is optimal, this stacks the cards and leads to the top card running much hotter than the bottom, and the fans cranking quite loud.

The manual also lists the option of running the SLI setup in the x16/x4 lanes- but would I experience a drop in performance? I'm using an EVGA HB Bridge.

Thanks so much.

 

[junkeymonkey]

NVidia sli / single card min spec is x8 amd x-fire can be one card at 4x

why when yopu look at motherboards that cant do x8 /x8 min its not sli compatible

that should be all in your boards manual under its gpu set up ??

foe some reason I cant get the manual from MSI ??

 

[bootcher]

Yes, the GPU dropping to x4 would not be very good as the limit on the lane would cause a bottleneck in the performance. I even think it would not be possible to run SLI in a x4 lane, as SLI specification demands x8 or higher lanes. Only xfire can be run on x4 lanes.

 

[christopherhammond87]

Got it, so I need to stick to the stacked configuration I have. Thank you!!!

If keeping them as-is, are there any water cooling options (preferably closed loop systems) that would help cool down the top card?

 

[junkeymonkey]

Z170A MPOWER GAMING TITANIUM

AMD 3-way CrossFireX technology support

NVIDIA 2-way SLI Technology Support

reason with amd you can use x8/x8/x4 for 3 card x - fire NVidia is x8/x8 only for a 2 card sli

your board is not x16, x8, and x4

it single slot used at x16 when 2 slots are use [sli] there x8/x8 if 3 are used it then x8/x8/ x4 with the 3ed slot being shared off the chipset if the 3 slots were all off the CPU then they would be x8/x4/x4 you cant exceed 16 lanes from the cpu on a 100 series board

now if you get a 2011 board you can get cpu's with more lanes


2 examples


PCI Express Configurations ‡ Up to 1x16, 2x8, 1x8+2x4 [16 only to be used ]

https://ark.intel.com/products/88196/Intel-Core-i7-6700-Processor-8M-Cache-up-to-4_00-GHz

[2011 ]
Max # of PCI Express Lanes 40 [motherboard manufacture decides how the boards are ''wired'' to use the 40 lanes ]

http://ark.intel.com/products/82931/Intel-Core-i7-5930K-Processor-15M-Cache-up-to-3_70-GHz

 

[krells]

Got it, so I need to stick to the stacked configuration I have. Thank you!!!

If keeping them as-is, are there any water cooling options (preferably closed loop systems) that would help cool down the top card?

This cooler would work with your card http://www.evga.com/products/product.aspx?pn=400-HY-5188-B1 .

 

[rcald2000]

+christopherhammond87 In answer to your direct question, yes you'd want your two GTX 1080 GPUs in a x8 / x8 configuration.

I've looked at the manual for your motherboard, but you need to confirm one thing with the manufacturer: If instead of using PCI_E2 and PCI_E4, what if you use PCI_E2 and PCI_E6? Would PCI_E6 then utilize x8 instead of x4. I don't know the answer to this question, but I wouldn't make any assumptions. I suspect that using a slot 2,6 configuration and leaving slot 4 empty didn't occur to the person writing the motherboard manual. Seriously, confirm that slot 6 can only be x4 and no greater.

 

[junkeymonkey]

hang on to see if the corsairs kit for the 1080's comes out ?

http://www.corsair.com/en-us/hydro-series-hg10-n980-gpu-liquid-cooling-bracket

and get this from it

http://www.corsair.com/en-us/hydro-gfx-gtx-1080-liquid-cooled-graphics-card

GTX 1080 GPU, and cooled with a CORSAIR HYDRO Series H55

http://www.corsair.com/en-us/hydro-series-h55-quiet-cpu-cooler


I got a evga hybrid and its great 45c max overclocked ? , but go to evga store and see how easy it is to get the hybrid kit for a 900 card ?? your not

so if my pump fails I cant get a new replacement for it maybe now at best a used one from e-bay [ thanks evga]

corsairs kits are still sold today all day everyday evga has me holding the bag and they will not warrant or back up the 10 series pump on a 900 card I was told do it at my own risk ..

kinda makes me wish I went with the corsair/ msi seahawk now

 

[christopherhammond87]

NVidia sli / single card min spec is x8 amd x-fire can be one card at 4x

why when yopu look at motherboards that cant do x8 /x8 min its not sli compatible

that should be all in your boards manual under its gpu set up ??

foe some reason I cant get the manual from MSI ??

You may have had to register to get to the support section of their site which has the manuals.

There are 3 lanes, the top is x16, the middle is x8, and the bottom is x4. When cards are placed into the top 2 slots (x16 and x8) the motherboard runs them as x8 / x8.

 

[christopherhammond87]

+christopherhammond87 In answer to your direct question, yes you'd want your two GTX 1080 GPUs in a x8 / x8 configuration.

I've looked at the manual for your motherboard, but you need to confirm one thing with the manufacturer: If instead of using PCI_E2 and PCI_E4, what if you use PCI_E2 and PCI_E6? Would PCI_E6 then utilize x8 instead of x4. I don't know the answer to this question, but I wouldn't make any assumptions. I suspect that using a slot 2,6 configuration and leaving slot 4 empty didn't occur to the person writing the motherboard manual. Seriously, confirm that slot 6 can only be x4 and no greater.

Right, that's exactly what I was hoping to ascertain. PCI_E6 is listed as x4 on the chart they provide, but seems pretty unfortunate to have that as the only option since it would pretty much exclude the lane as anything but a Xfire addition.

Chart: http://imgur.com/a/Nbis4
http://imgur.com/a/Nbis4

 

[rcald2000]

Yes, if they did designate PCI_E6 as only x4, it might have to do with it's proximity to the M.2 slot; they may share that bandwidth. But regardless, you should still check with MSI or maybe one of the Gamers Nexus guys. I'm very interested to know the answer.

 

[junkeymonkey]

'' You may have had to register to get to the support section of their site which has the manuals. '

if that's true then MSi gotten pretty cheesy . maybe they don't want you to look over the manual before you buy ??? lol ,,,,,,,

one thing to look at is what slotd may become disabled when you use a certain slot


then this thumbs down ?/

''•Slot layout not the best for multi-GPU use''

https://www.techpowerup.com/reviews/MSI/Z170A_MPOWER_GAMING_TITANIUM/12.html

thing is I see no one spelling out the slots ???

best I see like I said your slots pci-e 2 and pcie-4 are wired to the pcie lanes of the cpu the rest seem to share off the chipset and why it x8/x8/x4 = 16 cpu lanes and 4 chipset

that's all there is too that if all 3 were wired to the cpu then it would be x8/x4/x4 = 16 cpu pcie lanes only god thing I do see is nothing get disabled when using a certain slot

like from this motherboard

''The PCIe x1 slots (PCI_E1, PCI_E3) will be unavailable when installing an expansion card
in the PCI_E4 slot.


your manual on page 30 see what gets disabled

there not too clear on that but its clear on the cards slots 2 slots off the cpu at x16 single or x8/x8 sli

 

[renz496]

nvidia SLI will not work on slot with x4 config regardless of PCI-E version. even if PCI-E 3.0 x4 have the same bandwidth/speed as PCI-E 2.0 x8 SLI will not going to work on the former but it will on the latter. so your only choice with SLI is only x8/x8.

 

[rcald2000]

^ Agreed. But the question is, can slot #6 on this motherboard be x8? That is what we don't know.

 

[renz496]

^ Agreed. But the question is, can slot #6 on this motherboard be x8? That is what we don't know.

one of the easiest way probably by looking at the physical pin available on the slot? at least that's how it is with my gigabyte board. the first x16 slot have full pin. the second only half. and the last one which is rated at x4 the physical pin is only half from my second slot (x8). though his mobo probably configured differently.

 

[junkeymonkey]

it just as it stated in the manual on page 30 pci-e slot 2 is x16 single card x8 2 card combined wit pcie -slot 4 that only x8 no matter witch are ''wired' to the cpu that has total of 16 lanes slot 2 is all ways dedicated for x16/x8 under any configuration

to me that's good cause it could of been the 3ed slot pci-e 6 could of been wired to the cpu and with that the 2ed slot pci-e 4 would of been reduced to x4 when the 3ed slot is populated and rendering sli incapable ..

so as MSI has it they dedicated the 2 pci-e primary slots all to the cpu and are the only 2 slots shared with the cpu . you see that with z87/97

'' The three PCI Express 3.0 x16 slots are controlled by the CPU, with the first slot working at x16 when only one video card is installed, the first two working at x8 when two video cards are installed, and the first working at x8 and the other two working at x4 when three video cards are installed.''
Read more at http://www.hardwaresecrets.com/asrock-z87-extreme6-motherboard/2/#7xRSE1Aw5Msf9u2U.99

[that's my board and now why I look at this harder you see how I can lose sli capability with it ?? ] see your board as far as that goes to me is better .


the rest of the slots are wired to the chipset and max per slot off the chipset is x4 /x2/x1 that has 20 lanes that shared among the minor pcie slots , sata , usb

http://www.gamersnexus.net/guides/2099-intel-chipset-comparison-z170-h170-h110


now look at how a board with a PLX chip does for you

''On this motherboard, however, the four slots are controlled by the processor, using a PLX PEX8747 switch chip, thus all slots are PCI Express 3.0. So, the possible slot configurations are x0/x16/x0/x0/x0, x16/x0/x0/x16/x0, x16/x0/x0/x8/x8, and x8/x0/x8/x8/x8. All the PCI Express 3.0 x16 slots support both SLI and CrossFireX technologies
Read more at http://www.hardwaresecrets.com/gigabyte-z87x-ud7-th-motherboard/2/#46j3eP8zKrfZ6PCZ.99

 

[rcald2000]

+christopherhammond87 I took the liberty of contacting MSI tech support on behalf of your issue (626-271-1004 option 1 1 1). Unfortunately slots PCI_E2, PCI_E4 and PCI_E6 can only have the configuration x8 / x8 / x4. A GPU will of course be recognized and function in the PCI_E6 slot, but will only have x4 bandwidth. I had the technical support rep email my recommendation to the MSI engineering department. In my opinion, in order to allow greater space between the cards, that the x8 bandwidth should reallocated to the needed slot; either PCI_E4 and PCI_E6.

I wish that I had better news. Friendly regards.