X210 miniPCIe eGPU?

[L29Ah]

I've grabbed some miniPCIe riser kludge (https://www.aliexpress.com/item/3286164 ... 4c4d5byZaI), plugged it in my X210 (instead of the wifi card, as the other minipcie slot doesn't work for some strange reason; wrong BIOS settings?), plugged in my AMD HD7870 and the power supply, turned the PSU on, turned X210 on (the video card fans start spinning at this point), but i don't see the video card in `lspci`.
The riser and video card setup works fine with my Thinkpad X230.
What might be wrong with my X210 setup? Do i need to adjust any settings?
Have anyone else tried to bring eGPU up with a 51nb board?

[flyingfishfinger]

Make sure you turn off CLKREQ in the BIOS and ensure that pin 4 (CLKREQ) of the mini PCIE adapter is grounded, then it should work. Anything I've thrown at the bottom slot works, but admittedly I haven't done an EGPU

R

[L29Ah]

Make sure you turn off CLKREQ in the BIOS and ensure that pin 4 (CLKREQ) of the mini PCIE adapter is grounded, then it should work. Anything I've thrown at the bottom slot works, but admittedly I haven't done an EGPU

R

It isn't grounded, but does it even matter when CLKREQ is disabled in BIOS?

[flyingfishfinger]

It shouldn't, but it might. I would try grounding it & try again!

R

[L29Ah]

Not sure if grounding CLKREQ# helped, but the device gets attached with Hotplug enabled on Port4 in BIOS Setup, sometimes it takes time to appear in `lspci -H 1`, and after it appears, the kernel needs a gentle nudge to see it: echo 1 > /sys/bus/pci/rescan
Interestingly, it Just Worked™ on X230.
Maybe the top port link could use similar tactics, dunno.

[L29Ah]

A-and after another reboot it just stopped popping up.
I wonder if PCIe PHY can be made stronger, like with i915.edp_vswing=2 in case of eDP.

[L29Ah]

Forcing the PCIe interface to Gen2 speed in BIOS setup made it work reliably.
The gaming performance isn't stellar though. I'm not sure whether a narrow bus, or [censored] drivers, or anything else is the reason though.

[axur-delmeria]

Maybe a shorter cable would help?

[flyingfishfinger]

Gen3 probably won't work over the USB cables they're using there, you'll need properly shielded cables. My Thunderbolt project works fine at Gen3 using the ADT-Link stuff, it's kind of expensive but it seems to be so for a good reason. This could work, for example: https://www.aliexpress.com/item/4000944634410.html

R

[L29Ah]

Gen3 probably won't work over the USB cables they're using there, you'll need properly shielded cables. My Thunderbolt project works fine at Gen3 using the ADT-Link stuff, it's kind of expensive but it seems to be so for a good reason. This could work, for example: https://www.aliexpress.com/item/4000944634410.html

R

I wonder if a 30cm USB 3.1 cable would do the job. USB 3.1 pushes 10Gb/s after all while PCIe Gen3 is 8Gb/s.

[flyingfishfinger]

I doubt it. USB 3.x has extra differential pairs in it, separately from the regular D+/D- that are used in USB 2.0 (those are kept for "backwards compatibility"). You could maybe get a shielded USB 2.0 cable (which is a thing) though, that may help.

Did you try the same method on the upper slot (after reflashing the BIOS with the FIT changes I mentioned)?

R

[L29Ah]

I doubt it. USB 3.x has extra differential pairs in it, separately from the regular D+/D- that are used in USB 2.0 (those are kept for "backwards compatibility"). You could maybe get a shielded USB 2.0 cable (which is a thing) though, that may help.

Did you try the same method on the upper slot (after reflashing the BIOS with the FIT changes I mentioned)?

R

Not yet. I've tried with the tiny firmware header patch i derived, but that didn't work out.

Meanwhile i recall that i also disabled alternate functions of pcie in the pcie configuration in bios setup (not specific to a port).
darn, i wish there was a way to export/import/diff the bios setup config in a readable format.

[flyingfishfinger]

darn, i wish there was a way to export/import/diff the bios setup config in a readable format.

Yeah... that would be great. I also tried poking at kernel command line parameters (pcie_port_pm, pcie_pme etc) to no avail.

R

[L29Ah]

darn, i wish there was a way to export/import/diff the bios setup config in a readable format.

diff`ed complete listing of `efivars` after adjusting the bios configuration, and nope: the only difference is in the reboot counters or smth. At this point i'm not sure whether it makes sense to go on and decipher the stock bios behavior or switch to fiddling with coreboot.

[flyingfishfinger]

I don't think a diff of the BIOS will show changes to the firmware descriptor blobs, as modified with FIT. For coreboot the same applies, you still need to use the same descriptor blobs. Plus I've already tried a bunch of things with coreboot and I got the exact same errors / results...