1080 sli x8 x4 lanes; single 1080ti x4 lanes; 2080 x4 lanes; Limited length on PCIE_1. Your Opinion

Nov 3, 2018
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I am replacing my 1070 with one or two new cards. Due to space issues the only card that will fit in the PCIE_1 is a Gigabyte 1080 ITX. The second VGA Lane PCIE_3 has plenty of room. My budget is ~$1000. So here is the issue.

I can run 2 x 1080 in sli utilizing both x8 and x4 lanes.

I can run 1 x 1080 ti for $500 on the x4 lanes. 

I can run 1 x 2080 on the x4 lanes.

Motherboard:ASUS C7H wifi

Processor: Ryzen 7 2700x

SSD: 2x m.2 Samsung 970 pros x 0 Raid (not changing this for more lanes).

Right now I'm leaning towards the 2 x 1080 sli for the power and open lanes, but I'm afraid that I may miss some future feature which only the 2080 has. Unfortunatly, if running the 2080, I will lose some performance due to the lack of lanes. I could tolerate x8, but x4 for the primary video card???

FYI the top PCIE slot is limited in length due to water piping which cannot be rearranged or moved. Only the Gigabyte 1080 will fit, not even the Zotac 1080 ti mini:(

I welcome all helpful opinions.
 
Solution
Looking at the motherboard, the top two pci express x16 slots lanes come from the cpu. The 2nd x16 slot takes 8 from the first slot, which can then be shared with the m.2_2 socket. If you didn't need performance graphics you could load up both m.2 and get two m.2 converters for the pci express slots and have raid 0 for performance with raid 1 for redundancy, or raid 10 for a mirrored stripe with 4 drives. So a converter in top slot should mirror with m.2_1 easy since the raid controller can do 0/1/10 arrays. You'd use a 1030GT single slot GPU in the gen2 x4 slot at the bottom just for display if such a RAID array was needed.

Looks like m.2_1 and a converter in first x16 for raid 0 should be fine. and makes the 2nd x16 slot 8 lanes...

CrazyDingo

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May 1, 2015
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Sorry but that just doesn't sound right - can you not remove you're current cooling system and install a different system that gives you a better choice? Surely the cooling should be chosen to suit the graphics, not the other way around?!
 
Nov 3, 2018
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The PCH cooling is the problem. I did suit it to graphics, its just that I suited it to a 1070 mini card and now I feel like upgrading. The PCH's on the C7H seem to run slightly warm, but I guess it could be tolerable to delete that portion of the build.
 
Nov 3, 2018
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I checked with NVIDIA and they will run on x4 lanes. It simply requires a motherboard which is SLI compliant and 2 x16 slots (x8 lanes and x4 lanes)

 

kraelic

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Feb 12, 2006
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Nvidia would have made a huge turnaround then. When SLI was introduced the 6800s and 6600s with drivers before 70.90 would run SLI in a DFI lan party x8/x8 mode, and also work in a x16/x2 mode. Then nVidia coded the requirement of x8/x8 mode in the 71.xx drivers. Moving to X99 boards and the reduced 28 lane CPUs the x16 x8 x4 boards were two way sli capable and 3 way crossfire, there was a MSI X99 with x8 x8 x8 lane routing for 3 way SLI.

https://www.anandtech.com/show/1590/3
 
Nov 3, 2018
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I read a reply from NVIDIA stating that x4x4x4 was possible determinate on the motherboad. I have emailed them myself to clarify. I didn't read the rest of your statement, but I should have. I didn't even think about being able to get those 4 lanes back, but I could Image the current array. The only thing I will have to read into is how difficult it will be to raid 0 the PCIE_1 and m.2 at 3.0. Thats the only reason I chose ASUS in the first place as it was the only x470 which could Raid 0 Samsung 970s at full 3.0 speeds each. Anyways, awesome answer thank you.

 

kraelic

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Feb 12, 2006
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Looking at the motherboard, the top two pci express x16 slots lanes come from the cpu. The 2nd x16 slot takes 8 from the first slot, which can then be shared with the m.2_2 socket. If you didn't need performance graphics you could load up both m.2 and get two m.2 converters for the pci express slots and have raid 0 for performance with raid 1 for redundancy, or raid 10 for a mirrored stripe with 4 drives. So a converter in top slot should mirror with m.2_1 easy since the raid controller can do 0/1/10 arrays. You'd use a 1030GT single slot GPU in the gen2 x4 slot at the bottom just for display if such a RAID array was needed.

Looks like m.2_1 and a converter in first x16 for raid 0 should be fine. and makes the 2nd x16 slot 8 lanes again.
 
Solution
Nov 3, 2018
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Thanks again kraelic. Just an FYI. I decided to use a Aquacomputer Kryos PCIE adapter ( a little overkill), and after installation, my PCIE_3 is confirmed 8 lanes and I didn't even need to rebuild the ARRAY. I also ran a disk benchmark and speeds are just as fast as they were before. Great job kraelic.