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Lothos · ‎11-30-2020

I noticed this board comes with 3 PCIe x16 slots and only 1 PCIe x1 slot.

Under my old board which was a Crosshai VII it had an extra PCIe x1 slot. I was able to put a second video card (non-SLI so it was dedicated to a second monitor), a sound card an a WiFi 6 network card in those slots so the main video card still ran at x16 speed in slot 1.

What I am noticing is that this configuration does not appear to be possible with the Crosshair VIII Heor x570.

If I am reading the manual right, even if I put the sound card (or wifi) card in the PCIe x16_2 slot it will drop it down to x8 speed for both the 16_1 and 16_2 lanes.

So their is no way to get the 3 cards in.

Am I correct?

Does anyone have any ideas?

RedSector73 · ‎11-30-2020

Firstly there no graphics card that comes close to using x8 PCIE GEN4. Secondly there no graphics card that comes close to using x8 PCIE GEN3.

https://www.techpowerup.com/img/x5IOE9hplxgQwNWM.jpg
Not sure really what the issue is ?

Lothos · ‎11-30-2020

Was trying to maximize performance is all. I have a GTX 2080 currently and I am sure over the next few months I will upgrade to a 3080.

On my Crosshair VII x470 I did some benchmarks with the 2080 at x16 and x8 and there is a very small performance hit, but its there.

Was just trying to avoid that if possible!

RedSector73 · ‎11-30-2020

3080 is GEN4 PCIe doubt you could find performance hit x16 to x8. I can't find any video saying there is from benchmarking, I believe this will be non issue if you move to CH8 but I have no way to confirm this for you either, just my gut feeling.

So here is why I think it wont matter.
PCIe GEN3 x16 15.754 GB/s and x8 7.877 GB/s
PCIe Gen4 x16 31.508 GB/s and x8 15.754 GB/s
Source: https://en.wikipedia.org/wiki/PCI_Express

x8 provides GEN4 PCIe provides what full x16 PCIe GEN3 can deliver.

All video I can find suggest PCIe GEN3/4 has a 0 to 5% performacne gains and nothing about x16 to x8 GEN4 as a possible loss.

Lothos · ‎12-01-2020

RedSector73 wrote:
3080 is GEN4 PCIe doubt you could find performance hit x16 to x8. I can't find any video saying there is from benchmarking, I believe this will be non issue if you move to CH8 but I have no way to confirm this for you either, just my gut feeling.

So here is why I think it wont matter.
PCIe GEN3 x16 15.754 GB/s and x8 7.877 GB/s
PCIe Gen4 x16 31.508 GB/s and x8 15.754 GB/s
Source: https://en.wikipedia.org/wiki/PCI_Express

x8 provides GEN4 PCIe provides what full x16 PCIe GEN3 can deliver.

All video I can find suggest PCIe GEN3/4 has a 0 to 5% performacne gains and nothing about x16 to x8 GEN4 as a possible loss.

That is interesting, curiosity do you know what the maximum throughput that a 2080 and a 3080 use then?

Silent_Scone · ‎12-01-2020

Hi,

Having used a GEN 3.0 riser cable (@ GEN3) with an RTX 3080 on the CH8 and using GEN 4.0 conventionally, the performance was within margin of error.

13900KS / 8000 CAS36 / ROG APEX Z790 / ROG TUF RTX 4090

RedSector73 · ‎12-01-2020

This is test of bandwidth 2080 ti
https://www.gamersnexus.net/guides/3366-nvlink-benchmark-rtx-2080-ti-pcie-bandwidth-x16-vs-x8
and this is for 3080
https://www.kitguru.net/components/graphic-cards/dominic-moass/nvidia-rtx-3080-pcie-4-0-vs-3-0-scali...

I was kinda surprised you have found differences on your x470 motherboard and respectfully wondering if maybe config issue might be the cuase. If run userbench, and post link to the url of the results. https://www.userbenchmark.com/ and HWinfo screenshot the summary page for me and post it. https://www.hwinfo.com/download/ more than happy to have a look and see if something is up.

Lothos · ‎12-01-2020

RedSector73 wrote:
This is test of bandwidth 2080 ti
https://www.gamersnexus.net/guides/3366-nvlink-benchmark-rtx-2080-ti-pcie-bandwidth-x16-vs-x8
and this is for 3080
https://www.kitguru.net/components/graphic-cards/dominic-moass/nvidia-rtx-3080-pcie-4-0-vs-3-0-scali...

I was kinda surprised you have found differences on your x470 motherboard and respectfully wondering if maybe config issue might be the cuase. If run userbench, and post link to the url of the results. https://www.userbenchmark.com/ and HWinfo screenshot the summary page for me and post it. https://www.hwinfo.com/download/ more than happy to have a look and see if something is up.

The difference was very minor on 3DMark but it was consistent. When you benchmark x16 vs x8 with everything else equal I would loose about 50 to 100 points on the benchmark using an EVGA 2080

The links you provided, was not sure what I was looking for in there. Wanted to figure out what was the theoretical max the 2080 and 3080 could do and if it was close to these specifications

PCIe GEN3 x16 15.754 GB/s and x8 7.877 GB/s
PCIe Gen4 x16 31.508 GB/s and x8 15.754 GB/s

Question on Crosshair VIII Hero (not wifi)