ASUS WRX90E-SAGE x8/x8 Bifurcation

Can anyone verify that the Asus WRX90E-SAGE board has x8/x8 bifurcation as an option? The manual seems to suggest that there is only x16, what I think is x8/x4/x4, and x4/x4/x4/x4 (what ASUS calls RAID?), but no x8/x8.

In contrast, the WRX80E WIFI that I have also does not list it in the manual, but my BIOS does have x8/x8 as an option. I also have a WRX80E WIFI II that both has it in the BIOS, and also lists it in the manual. So there seems to be no correlation.

According to this video: https://www.youtube.com/watch?v=iFgDxStELkA 27 there is no x8/x8 as he is going through the BIOS options. Sucks if ASUS removed a feature that was on the earlier version. But he also had an early version of the board, and they may have added it back in a later BIOS update.

Would appreciate any input from current owners (I know there aren’t many).

I would expect 6 of the PCIe slots to have x8/x8 available if it is implemented, because they nerfed the 7th PCIe slot on the 90E compared to the 80E (it is only x8 instead of x16). Not sure why they did that, guess to add dedicated M.2 slots without sharing bandwidth with U.2/SlimSAS instead.

I’m running 13 GPUs on the 80E and would like to transfer that config over to 90E, but x8/x8 is a necessity!

Thanks, will wait and watch I guess. Sucks that ASUS didn’t carry it forward from the previous generation.

I can’t even rely on the BIOS update logs to tell me if/when they add the feature. There is no mention of it in the logs for 80E, and yet I know they added it in one of the updates.

Only the top slot has x8x4x4? I thought all slots had x8x8x8x8 and x8x4x4.

If you do have any success contacting or feeding back something to ASUS, it would be great!

Meanwhile, I do see some success using PLX switches without Bifurcation support, but that does complicate the setup a lot.

I have had not had much success communicating things like this to them either. There has to be some way to talk to the EPYC board support team or something, but I haven’t found it. Good luck!

External PLX switches do seem to work to bypass any type of PCIe connection that the board does not support, including muxing PCIe Gen4 devices into Gen5 without losing bandwidth. Like this one: PCIe gen5 Switch 52-Lane Mircochip Switchtec PM50052 PLX – C-Payne PCB Design 33
But they are pricey.

Is it slots 4,5,6,7 again that has the built-in re-drivers on the WRX90?

Those have honestly been a huge pain to deal with in the WRX80, ASUS probably didn’t use very high quality re-drivers. I’m beginning to see the wisdom in packing more MCIO ports closer to the CPU instead of slots. You can drive or re-time the MCIO however you need later.

Oops, my bad! Yes I meant 5,6,7, it is the same with the WRX80 versions also.

Also, the C-Payne PCIe switch I mentioned earlier has an issue with ADA-class NVidia GPUs presently: they are forced into PCIe Gen3. Christian tells me there is a fix on the way via a firmware update soon.

EDIT: The software fix did it, now I can do better than x8/x8 and get full x16/x16 gen4 on x16 gen5 with no bifurcation.

That still works to bypass bifurcation: Gen3 x16 = Gen4 x8, which is what the bifurcation would do on a Gen4 platform at least. The fix would be needed to take advantage of Gen4 x16 on Gen5 platforms.

Fingers crossed! And if asked, the answer is 8x/8x in all 16x slots!

Let’s hope crnoddin’s request gets some attention then! I too returned my bord so someone else would need to verify if they ever add it. If you are desperate, external PLX switch still works, though is additional cost.

I suspect they should never have tried to push everything with full PCIe slots. A lot of the server boards can push that much IO just fine with Epyc boards using MCIO where needed. But they may think of the WRX platform as some kind of prosumer thing, and want to provide full PCIe slots for easy compatibility.

Good luck!

I am personally not thrilled to see the question “Why did you want x8/x8?” in today’s day and age though, from the board maker no less.