Say NO to the Paywall of PCI-E Bifurcation

[zombielinux]

On 1/9/2023 at 3:45 AM, distorter said:

Have been searching for this info for sometime, thanks for the post. I knew my CPU supported PCI-E Bifurcation (Skylake i7/6700) but my motherboard(Q170m) didn't.

 

@grayxu The grounding pins are quite far from the CFG 5 and 6 points for the 6700. So I assume you would need to do this on the socket instead with a tiny bit of wire?

 

In your case, I'd probe around the motherboard and see where CFG[5] pops up on a trace, capacitor, resistor, something, and ground from there.

[forbiddenera]

This is awesome. <3's for OP. Shame half the responders have nfc wtf.

 

Was curious how possible this might be; not having easy access to proper datasheets doesn't help. My BIOS doesn't have any bifurcation options but does have a hidden CPU PCIe Lanes Configuration that I was hoping would split the CPU slot to x8x8 or something, but wasn't sure how that might work out because it seems like it's usually geared towards splitting across multiple physical slots on a board, where I only have one x16 CPU slot.

 

So, because of this thread I have some hope the option could do what I wanted and, apparently, alternately now have a secondary way to do it.

 

Neat.

 

For details: my board has a x16 CPU slot then 1*x16 (x4 electrical) 4*x1 PCH slots (MSI Z390-A PRO) and I have a GPU (2070 Super) in the main x16 slot and another GPU (3060) in the secondary x16 slot (which I originally thought/assumed was at least x8).

 

Both GPUs coolers block x1 slots where I only have one x1 actually exposed. I've found a small bendy x1 riser that I stuffed under the 3060's shroud to extend one out.

 

So then I also have a Thunderbolt card and an M.2->PCIe card, both able to use x4 but stuck at x1.

 

Thunderbolt card does work but seems to occasionally have some weirdness/issues which is possibly caused by my board expecting it to be installed in the second x16 (which is only x4) slot.

 

I don't think that running the 2070S at x8 would make a noticeable difference; I didn't even realize the 3060 was at x4 and not x8 until now anyway and didn't notice any major performance issues with it, though it is a secondary card.

 

Splitting the main CPU x16 to x8x8 would allow me to run both GPUs at x8 and free up the second "x16" (x4 electrical) for the Thunderbolt card as MSIGOD Intended. Also, since I'd need to get creative with risers and such to make it work physi-electrically, I'd free up any x1 slots covered by GPU coolers (I'd probably make or 3D print some kind of GPU chassis for them or at minimum swap to a case that allows vertical and horizontal PCIe mounting, though that only really would give a spot for one of the two GPUs)

 

This would also allow me to run the second M.2 drive in a Thunderbolt enclosure (which I could do now, but the Thunderbolt is in an x1 slot, so it'd be slower if anything), freeing up an x1 slot and allowing it potentially (depending on connected Thunderbolt devices) more bandwidth than the x1 could manage.

 

The alternative is putting the secondary GPU in one of the x1 slots and the Thunderbolt in the second "x16" (x4 electrical) slot, which is definitely easier than BIOS hacking and everything else and not entirely the worst option as I mostly only use it for extra screens but I haven't been able to bring myself to do this yet, not for much good reason though; MultiGPU in DX12 etc. is never really implemented anywhere and other than stuff like Blender or other rendering/dGPU/CUDA is the only other major use case which I think, for most things, compared to gaming, is likely light on bus bandwidth usage... but why do the easy thing when I can hack stuff instead?

[mirddes]

On 12/24/2023 at 11:54 PM, forbiddenera said:

This is awesome. <3's for OP. Shame half the responders have nfc wtf.

i honestly can't fathom how they can't fathom what OP is describing, it's the literal definition of bifurcation.

aliexpress has countless options for x8x8, x8x4x4, and x4x4x4x4 risers, all for absurdly cheap prices.

being able to use these on older platforms will really enable getting the most out of ITX builds like my mum has (modded Awyun A1-1001, 3rd gen intel i3).

[mirddes]

 

 

I just have two very important questions; what is the silver paste used to bridge the pads, and how did you apply it?