The PCIe x16 capacitor mod is the only hardware step in the usual CMP 170HX unlock: soldering 24 missing capacitors takes the link from x4 to x16 on both the 8 GB and the 10 GB card. It is Proven, meaning a second person reproduced it with numbers, and it mostly helps prefill, model loading and tensor parallel.
What the mod does
All 16 lanes are routed on the board, but the AC-coupling capacitors for lanes 4 to 15 were never fitted. The mod changes link width only, never the PCIe generation: a modded card with no unlock reports Gen1 x16, and with cmpunlocker it reports Gen2 x16.
Parts: 24 capacitors in 0402 size, 220 nF, X7R; order at least 30. One confirmed part is Samsung Electro-Mechanics CL05B224KO5NNNC, per @globalapathy (October 11, 2026).
Results
@anon33anon reproduced it on three cards on October 15, 2026: two trained x16 at once and the third only after its suspect capacitors were redone. An x8 result means a bad joint, not a hardware limit.
Gen2 x16 measured 6.63 to 6.67 GB/s. On a single 40 GB card, going from x4 to x16 gave about 4x prefill but only about 3% more decode, per @exile_1ck (October 7, 2026). Without the mod, x4 is the most any PCIe generation reaches, including Gen3 on a 10 GB card, per @lxtend and @djpandaman (October 17, 2026).
Risks
Several points carry a Warning, the badge for something that damaged hardware. Hot air at normal flow blows 0402 parts off the pads, over-preheating can bend the board or break internal traces, and removing the shroud can crack the die or HBM.
The electrical risk is low, but the skill bar is high: if you have not soldered 0402 parts before, practise on a dead board or have a shop do it. No card has been reported killed by the mod itself.
Related hardware fixes
HW Power Brake: some boards and risers assert the PWRBRK# signal on edge pin B30, which holds a card at about 80 to 88 W and 1140 MHz, roughly 4x slow. Covering pin B30 with high-temperature tape fixed it, per @deejay9983 and others (July 30, 2026); this is Proven. Check that nvidia-smi shows "HW Power Brake Slowdown: Active" before you tape anything.
NVLink on the 10 GB card: @ghostinthedatacenter_87281 fitted the missing NVLink parts to a 10 GB card and wrote on October 30, 2026 that the card is unlocked, but no trained link exists yet, so it is Reported, meaning one person's result. The 8 GB card has no NVLink path.
The CMP 90HX takes the same 220 nF capacitors, but its pad orientation differs from the 170HX.