Gen5 NVMe sharing bandwidth with PCIe x16 slot

[DarkFury]

Ok a scenario i've been scratching my head for a while now, please can someone explain.

I'm upgrading soon to a Aorus z790 Master motherboard with an i9 13900KF and was thinking going for a
1TB Gen4 NVMe drive for OS in 2nd M.2 slot
and a
2TB Gen5 NVMe drive for games in the top M.2 Gen5 slot.

So from what i've looked into via the Manual for this motherboard I know if you occupy the top M.2 slot it'll force the PCIe x16 slot to run at x8... would that be "gen5" x8 i assume or would that be "Gen4" x8?

I know Gen5 x8 is the same speed as Gen4 x16 so won't lose GPU performance on say a RTX4090 but if it runs at Gen4 x8 i'll be throwing some performance away.

So will the PCIe x16 slot run at Gen5 x8 or Gen4 x8? i'm confused.

Thanks

 

[Dg834man]

It will run 8x lanes, the gen will depend on what the card supports.

 

[Tetras]

So from what i've looked into via the Manual for this motherboard I know if you occupy the top M.2 slot it'll force the PCIe x16 slot to run at x8... would that be "gen5" x8 i assume or would that be "Gen4" x8?

I know Gen5 x8 is the same speed as Gen4 x16 so won't lose GPU performance on say a RTX4090 but if it runs at Gen4 x8 i'll be throwing some performance away.

So will the PCIe x16 slot run at Gen5 x8 or Gen4 x8? i'm confused.

It will run at PCI-E Gen 5, with 8 lanes, however the 4090 only supports PCI-E 4.0, so it will be Gen 4 with 8 lanes.

The performance loss in TPU's scaling article was a few %, so it is not a big deal.