Asus Maximus XI Extreme

[Devastation14]

Hello everyone,

I just wanted some clarification on an upgrade I am looking to build. I want to upgrade to the i9 9900k with the asus maximus extreme board. I will be using sli 1080ti gpus, I wanted to know the restrictions I would experience when it comes to the m.2 slots.

Any advice would help,

Thanks

[Vlada011]

Welcome to ASUS ROG Forum,
As you know i9-9900K have 16 PCI-E lanes, that mean SLI will work x8.
M.2 and other controllers are probably connected to PCH with 24 Gen 3 PCI-E lanes. Small PCI-E slots x1 and x4 are connected to PCH as well.

I didn't saw board and what they implement inside and I hope no more Controllers who use PCI-E lanes from CPU.
That would be disaster because than speed would drop even more if only single PCI-E lanes is used from processor.
But all previous motherboard left CPU 16 lanes for GPU to work on full speed,
same is with Extreme and your SLI will work on x8 speed if you use proper slots on motherboard planned for that.

Whole platform is not planned as main choice for SLI configurations but work.

[Vlada011]

Motherboard manufacturers sometimes make big mistakes with mobo layout.
Example with X99 and X299 no one had idea to allow customers benefits of CPU with 28 PCI-E lanes.
That mean to connect x4 slot one or two to CPU.
If customer use x16 slot no matter how many lanes device use speed of GPU drop on x8, because 16+16 is 32 and CPU have only 28.
But if you have 28 lanes and GPU use 16, you have option to install M.2 Gen 3 to use CPU lanes, and one x4 slots where customers could use Intel 750 SSD or PCI-E SSD example and speed of GPU will not drop. With X299 Gen3 PCH allow better posibilites, but with X99 Gen 2, you could use PCH eventually for sound card but several PCI-E lanes are free and big slots can't be used and no such advance motherboard to recognize how many lanes your device installed in x16 slots use. She immediately recoznie as all 16 or 8 PCI-E lanes even if you put sound card there or x4 USB 3.1 card.
My RVE10 is only mobo I think with x1 and x4 slot in same time.
And in theory have enough PCI-E lanes to M.2 x4 CPU, PCI-E SSD x4 CPU, GPU x16 and Sound card x1 PCH work in same time on 28 lanes CPU.
I didn't tried and can't say is it possible, but could be build.

[pndiode]

According to the manual: A single GPU in Slot PCIe_x16_1 will run at x16, but will run at x8 with a GPU also in PCIe_x16_2 which will also run at x8(SLI).

Manual reads as though you will not lose/drop any SATA6G ports unless you use the PCIEX16_3 slot (x4 mode). So, no SATA6G ports lost if using both M.2_1 and M.2_2 sockets.

However, I cannot explain what affect the BIOS CPU PCIE Configuration Mode:
Configuration options: [PCIEX16_1 + PCIEX16_2] [DIMM.2_1 + PCIEX16_2] [DIMM.2_1 + DIMM.2_2] has on (DIMM.2_1) PCIEX16_2.