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ROG CROSSHAIR X870E HERO confuse documentation about PCIe lanes

nanatt
Level 7

Regarding the ROG CROSSHAIR X870E HERO  PCIe lanes:

nanatt_0-1735504566663.png

I found comments on reddit here and here indicating that ANY use of M.2_2 slot will reduce the PCIEX16_ lanes...

But the documentation doesn't say anything if using M.2_1 and M.2_2 affects the lanes:

** When you use both PCIEX16_1 and PCIEX16_2, PCIEX16_1 and PCIEX16_2 will run x8.
*** When M.2_3 are enabled, PCIEX16_1 will run x8, and  PCIEX16_2 will run x4.
**** When M.2_2 and M.2_3 are enabled simultaneously, PCIEX16_2 will be disabled.

My intention in acquiring this motherboard is to use 2X GPU's and also 2X M.2 GEN5.

I'm aware that the GPU's will run at x8/x8, my doubt is:

If I use = ONLY = the M.2_1 and M.2_2 slots, the PCIe lanes available to the GPUs (PCIEX16_1, PCIEX16_2) will be reduced making them to run at x8/x4, or potentially disable PCIEX16_2 entirely?

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EdgarVanEkart
Level 7

According to the Manual, in theory you could use M.2_1 and M.2_2  and still run 2 GPUS a X8, but the manual isin´t quite clear as you mention.