passthrough Planning on using my GTX 1060 as 2nd GPU for VMs. Would running on x8 be PCIe 3.0 x8 or PCIe 4.0 x8?

[YamiYukiSenpai]

I am planning on having a dual GPU setup on my next build, with my primary being RX 6800XT, and the secondary (used for VMs) would be GTX 1060 6GB.  When the PCIe 4.0 slot is on x8 mode, would the 1060 be outputting on x16 (because it's on PCIe 3.0, instead of 4) or x8?

 

Also, how much of an effect would running on PCIe 4.0 x8 on a new GPU, like the 6800XT?

 

For reference, here's my planned build (some I purchased already):

 

PCPartPicker Part List: https://ca.pcpartpicker.com/list/ywQMGq

CPU: AMD Ryzen 9 5900X 3.7 GHz 12-Core Processor  (Purchased For $599.99)
CPU Cooler: Noctua NH-D15 chromax.black 82.52 CFM CPU Cooler  ($139.94 @ Amazon Canada)
Motherboard: *Gigabyte X570 AORUS XTREME EATX AM4 Motherboard  ($849.99 @ Amazon Canada)
Memory: G.Skill Ripjaws V 64 GB (2 x 32 GB) DDR4-3600 CL18 Memory  (Purchased For $364.99)
Memory: G.Skill Ripjaws V 64 GB (2 x 32 GB) DDR4-3600 CL18 Memory  ($424.37 @ Amazon Canada)
Storage: Samsung 860 Evo 500 GB 2.5" Solid State Drive  (Purchased For $0.00)
Storage: Samsung 860 QVO 1 TB 2.5" Solid State Drive  (Purchased For $0.00)
Storage: Samsung 980 Pro 2 TB M.2-2280 NVME Solid State Drive  (Purchased For $369.99)
Storage: Samsung 870 QVO 8 TB 2.5" Solid State Drive  ($869.99 @ Amazon Canada)
Video Card: Sapphire Radeon RX 6800 XT 16 GB PULSE Video Card  ($1953.52 @ Amazon Canada)
Case: Lian Li O11D XL-X ATX Full Tower Case  ($317.37 @ Amazon Canada)
Monitor: BenQ EW3270U 31.5" 3840x2160 60 Hz Monitor  (Purchased For $400.00)
Monitor: Asus TUF Gaming VG27AQ1A 27.0" 2560x1440 170 Hz Monitor  (Purchased For $369.99)
Custom: Antec Signature Series ST1000, 80 PLUS Titanium Certified, 1000W Full Modular with OC Link Feature, PhaseWave Design, Full Top-Grade Japanese Caps, Zero RPM Mode, 135 mm FDB Silence & 10-Year  (Purchased For $250.00)
Custom: ZOTAC GTX 1060 6GB (Purchased)
Total: $6910.14
Prices include shipping, taxes, and discounts when available
*Lowest price parts chosen from parametric criteria
Generated by PCPartPicker 2021-12-27 04:36 EST-0500

[--SID--]

What motherboard?

[YamiYukiSenpai]

5 minutes ago, --SID-- said:

What motherboard?

Haven't decided yet.

 

I'm still reviewing all of my options, but from what I gathered, the best I can go for with AM4 X570 mobos would be x8/x8 (which some don't support, I think).

 

I could be wrong with that assumption cuz I just found an X570 Aorus Master to be able to dedicate x16 on 1 slot and x8 on another (unless I'm reading it wrong).

[--SID--]

If the motherboard split the CPU lanes in 2x 8 to the 1st and 2nd PCI-e slot both slot work at PCI-e3.0 or 4.0. With a gen4 GPU in the 1st slot my experience is that a gen3 GPU won't work in the 2nd slot. Also the 1st slot has to work at gen3. One option is to buy a motherboard with a 3rd physical PCI-e x16 slot that's wired from the chipset and use it for the GTX 1060. Other option is a CPU with igpu and use the igpu for VM.

[YamiYukiSenpai]

16 minutes ago, --SID-- said:

With a gen4 GPU in the 1st slot my experience is that a gen3 GPU won't work in the 2nd slot. Also the 1st slot has to work at gen3. One option is to buy a motherboard with a 3rd physical PCI-e x16 slot that's wired from the chipset and use it for the GTX 1060.

thanks for the warning.  I didn't know that.

[Alex Atkin UK]

27 minutes ago, YamiYukiSenpai said:

thanks for the warning.  I didn't know that.

Me neither, I'd kinda like a second opinion as that seems a utterly stupid design flaw if true.

I'll have to test it out on my own system at some point.