Confused about SLI/Crossfire specifications

[axlrose87]

I am comparing 2 different Z270 motherboards that both claim to support them, but what does " 16x/0x/4x or 8x/8x/4x" configuration mean? Ideally wouldn't you want them to run 16x/16x?

Thanks for any help, I'm new to multi-gpu setups.

 

[Krteq]

...what does " 16x/0x/4x or 8x/8x/4x" configuration mean? Ideally wouldn't you want them to run 16x/16x?.

It's describing how PCI-Express lanes are distributed by PCI-Express controller.

For single card - 16x/0x/4x means 16 lanes for first PCI-Express slot, no lanes for second and 4 lanes for PCI-E 4x slot
For MGPU - 8x/8x/4x means 8 lanes for boths graphics cards and 4 lanes for PCI-E 4x slot

16x/16x/4x configuration isn't possible because PCI-Express controller doesn't have to many lanes available.

 

[Bouowmx]

CPUs for Intel Z270 provide 16 PCI Express lanes. The Z270 chipset itself also provides 24 lanes, connected to CPU via PCI Express 3.0 ×4.

"16/0/4" means 1 slot with 16 lanes to CPU, and 4 to chipset, a setup only for AMD CrossFire (Nvidia SLI requires 8 lanes for each GPU). GPUs connected to chipset are not ideal since they share bandwidth with everything else connected to chipset.

"8/8/4" means 2 slots with 8 lanes each to CPU, and 4 to chipset, a setup for both 2-way AMD CrossFire and Nvidia SLI. 3-way AMD CrossFire is possible, as described above.

Some motherboards like Supermicro C7Z270-PG have a switch that provides 4 lanes with 16 lanes each to CPU.

 

[axlrose87]

Thanks for the replies, I was comparing the MSI Z270 SLI PLUS and the MSI 270 gaming M3 and found that confusing. Appreciate it!