hi i am looking to build a home lab server. and i am totally new to this field.

i am currently looking for two motherboard and i am curious their compatiablity with MULTI gpus support under one os (linux or ubuntu). which means i want to use their totally gpu power at one task, just like using one gpus.

my desired task is to use at least two nvidia rtx 4090 gpus at their full speed and bandwidth under one system. is that possible?

  1. cheaper: Pro WS W790-ACE (https://www.asus.com/motherboards-components/motherboards/workstation/pro-ws-w790-ace/)
  2. expensive: Pro WS W790E-SAGE SE (https://www.asus.com/motherboards-components/motherboards/workstation/pro-ws-w790e-sage-se/techspec/)

these two motherboards are similar except for the capablity of Expansion Slots, as my understanding and my usage, that would be the max capability gpus usage.

in here i will list the specs of 1. Pro WS W790-ACE (copy from website):

Expansion Slots:

Intel® Xeon™ W-3400 and W-2400 Series Processors5 x PCIe 5.0 x16 slot(s) (supports x16, x16, x16, x0/x8, x16/x8 modes)* Please check the PCIe bifurcation table on the support site (https://www.asus.com/support/FAQ/1037507/).- To ensure compatibility of the device installed, please refer to https://www.asus.com/support/ for the list of supportedperipherals.

i asked gpt4 how many gpus i can use at the same time running at full bandwidth under ons system.

i got this:

Second Motherboard:

With either an Intel® Xeon® W-3400 or W-2400 Series Processor, it provides 5 PCIe 5.0 x16 slots. However, when all slots are populated, the configuration becomes x16/x16/x16/x8/x8. This means you can run three RTX 4090 GPUs at full PCIe 4.0 x16 bandwidth, and if you install a fourth GPU, it will run at x8 bandwidth, which is not the full bandwidth for a 4090 GPU.

is that correct and concise in the real case?

my questions is about the multi GPUs supports. as a person, i dont have money to buy a100/h100. i want to use multi 4090 as my workload and thats enough for me.

is this gpt4 answer correct? and can i achieve using multi 4090s with this motherboard?

thank you guys soo much.