Lenovo M920Q and M720Q PCIe x8 bifuration to x4x4 hardware mod by soldering missing components to the board.
*** It looks like this might work, placeholder, WIP. ***
Referring to post on STH, M720Q/M920Q models have the x8 PCI-E slot directly wired to the CPU.
Looking at soldered SMD components and board schematics, I see board is in CFG[6:5]:1:0" configuration, which is "10 = 2 x8 PCI Express" mode.
This makes sense, we have lines 0-7 in slot available. Goal would be to make "CFG[6:5]:0:0" configuration which will give "00 = 1 x8, 2 x4 PCI Express" mode.
After that, need to reverse PCIe lines (0-7 --> 7-0) with CFG[2]:0 configuration which should give us x4x4 lanes. This looks too easy to be true, need some testing...
Does not work with Supermicro AOC-SLG3-2M2. Now ordered this x8 adapter for further testing https://www.amazon.de/dp/B09MSB4TXT
placeholder, wip