Question Z790 Dark Hero question slot's, shared bandwidth

[wengang1]

Hi all.
I have one other question about the Z790 Dark Hero. I've pretty much settled on this board for my next rig, but I'm just trying to hammer out potential issues.

I read that "that M.2_1 shares bandwidth with the second slot. When enabled, the bottom PCIe slot is disabled, and the top slot breaks down to PCIe 5.0 x8."
I might have read it on this site.

I'm wondering if that is the main M.2 slot, and if I use it, I'll lose the use of the bottom PCIe slot (leaving only the top one which is where I plan to put the video card) and the video card slot will be in a reduced performance state.
Otherwise, if I don't use this slot and use a different one for my OS drive, will I get diminished performance of the OS?

It sounds like a bad design concept to me. Does anybody have more information/experience on this?

Thanks.

 

[Lutfij]

I read that "that M.2_1 shares bandwidth with the second slot. When enabled, the bottom PCIe slot is disabled, and the top slot breaks down to PCIe 5.0 x8."
Yes it's stated on their spec'd page for the motherboard;

ROG MAXIMUS Z790 DARK HERO | Gaming motherboards｜ROG - Republic of Gamers｜ROG Global

The ROG Maximus Z790 Dark Hero makes builds soar with 20+1+2 power stages, hyperspeed DDR5 support and the latest PCIe® 5.0 connectivity. It features five M.2 SSD slots with heatsinks, Intel® Wi-Fi 7, Thunderbolt™ 4, USB 20Gbps support, AI Overclocking, AI Cooling II, AI Networking, Two-Way AI...

rog.asus.com

https://dlcdnets.asus.com/pub/ASUS/mb/LGA1700/ROG_MAXIMUS_Z790_DARK_HERO/E22500_ROG_MAXIMUS_Z790_DARK_HERO_EM_WEB.pdf?model=ROG MAXIMUS Z790 DARK HERO
on the table in page XV.

Otherwise, if I don't use this slot and use a different one for my OS drive, will I get diminished performance of the OS?
If the drive you wish to drop into the slot is meant for the OS, you won't be able to tell the difference(in real world applications/scenarios) between a PCIe5.0 or a PCIe4.0 drive when next to a PCIe3.0 drive.

I've pretty much settled on this board for my next rig
That being said, if you need your first PCIe slot to be running a x16 lanes, you should look into another board/platform or have the OS NVMe drive on another slot on the board you've seemingly settled on since the rest of the slots don't share bandwidth with eachother(M.2_2/3/4/5) nor the other slots on the board.