Hello everyone! New to this forum and looking to get some assistance. I’m attempting to setup a x8/x8 bifurcation, ideally on slot 1. I’ve tried multiple tools, but at this point I’m hitting dead end after dead end. Since bifurcation isn’t included by default in the BIOS, it seems to be fairly difficult.
Version 4701 - 2025/01/16
Is this even possible to accomplish? If someone can point me in the right direction that would be great. I’m never one to look for a free ride but I’ll take that too at this point if someone can assist… LOL.
I’m attempting to get an accelerator card working designed to run 2 by x8 (single x16 slot). I have the first x8 lane recognized in the OS, but the second is not. I’m assuming this is due to bifurcation not being an option by default.
Thanks in advance!
Whats wrong with the Asus claims…
or seven x16/x8/x8/x8/x8/x8/x8) *2
*2 Please refer to the block diagrams in the Appendix for more details in the manual.
Appendix A1 & A2 pages…
No cpu model was pointed regarding available lanes.
No BIF is advisable on Slot1 but 3/5/7 are available.
Thanks for the reply. Are you saying that I can mod the BIOS to support x8/x8 on slot 3? Or that the PLX switches will support it out of the box?
I just tried slot 3 and it is still showing up as a single x8 instead of x8 *2 (Ubuntu).
No, im saying that you need to verify the tech specs of that “accelerator card designed to run 2 by x8 (single x16 slot)” card, that we dont know nothing… and talk to the Vendor/OEM how to/specific config…as don’t recall seeing a “Standard” motherboard PCIe using the x16 signal but split in 2 x8 ACTIVE signal on all lanes, the PLX chip makes re-route of unused lanes so… i could be wrong and still didn’t see all that is possible in this “world”.
Wait for other users POV, regards.
Thanks, I appreciate your responses. This is the card:
It states on the spec sheet x8 *2 but only has one x16 slot and is showing degraded in the OS. I assumed that was meant to be used with a bifurcation based motherboard, but I could be wrong in my understanding of the card’s functionality.
I don’t see PCIe BIF as requirement, on the PDF… i do see lanes… and still we don’t know how many available on your system due to no CPU specified.
Is this a lack of pcie lanes resources as they are taken by other devices attached…
By logic…if the card seats on a PCIe full active x16 signal…should work? OS used aside…
Again… besides slot 1, 3/5/7 can do x16…how does it comunicates on those?
That mb should have settings to split the pcie lanes but when splited the remaining lanes are re-routed as avaiable ones, again i cant recall one that has settings to split and still letting the remaing signal active, or a mod of such kind.
I dont hink you have the hw platform class, for this kind of card, looking in the web on some implemented systems…like the Dell EMC DSS 8440
Im out of this…sorry but it’s out of my league.
Sorry for the lack of details, the CPU is the 10980-XE (48 lanes). Which should have enough lanes for what I currently have plugged into the motherboard.
I appreciate your help, yes this is a card designed for server class systems. Hence the headaches I’ve been experiencing. Unfortunately Graphcore provides no end user support only for OEMs.
I was just hoping to get a BIOS mod to be able to split one of the slots with x8/x8 bifurcation to test and see if that resolves my issue.
I can run the card in degraded mode for now, if no other solutions become viable.
Thanks again!
But the board already splits it… as “regular” common and know desktop BIF
Does it matter if the motherboard “knows” to give it x8 *2 or not by what type of card it is, or is it based on what the card requests? Since I can’t see the PCIe lane allocation in BIOS (only for the GPUs), there is no way for me to know for sure if this is a hardware or OS/Driver issue. I can only confirm lane speed from Ubuntu at the moment.
Edit: I can see in BIOS the Graphcore card is showing as x8, so this is not an OS/Driver issue.
Thas exaclty your issue… what signal/requests the card passes to the system board and im afraid these standart boards cant do it.
Yeah, I was thinking the same myself. I’ve already come to the conclusion before posting here, I’ll probably run the card in degraded mode for testing purposes.
I appreciate you getting back to me, I’ll definitely post any updates if I come up with something.
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So it looks like the issue I have is with the PLX chip - PEX 8747 switches on this motherboard. I was able to get the Socket Config exposed in BIOS with the help of another on this forum. However, that does not let me access the PLX switches themselves. Since none of the PCIe slots are directly CPU connected, this is currently the issue.
I’m seeing to change the port configuration on the PEX 8747 switch requires physical hacking of the EEPROM. Unless of course there is someone who found another way to access these at a BIOS level.
As of now all the PCIe slots on this motherboard are locked behind the “Black box” that is the PEX 8747 chip/switch.
You want to change the OEM design of the mb, from PCIe connected to PLX controller to CPU attached… i may be foolish writing this, but do you have any ideia what you’re asking here?
Ask that user that helped you… what’s his opinion on the subject… I’m really CURIOUS about the answer…
You’re not foolish at all. I just didn’t properly understand how the motherboard worked, and the user that helped me didn’t understand what I was trying to do either.
I just explained to them and shared with them the card I was trying to use. I just had no idea this particular card needed so much fine tuning to get it working… even at a server level it probably expects root ports as opposed to bifurcation.
I just came back to let you know what I’ve discovered with the card, and in case it comes up for anyone else. Basically, if you can use 1x processor on this card you are lucky to even get that working. I even had to re-write the driver just to get the 1x processor working.
Thanks for looking into this for me here, I learned a lot along the way. Mainly what NOT to do when looking for hardware… LOL.
As i said before, browsing a little on the web on platforms using this card… its really no close to an ordinary consumer mb, its very specific…it’s not a case of fine tunning, all the best.
I figured what you were saying was true, I just wanted to do some additional poking around. I did learn along the way. Thanks again!
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