NVLink
More actions
| Theory 8 GB and 10 GB | |
| Driver | n/a |
|---|---|
| Unlock build | none public |
| Steps | NVLink |
| Source | Discord message |
| Confirmations | None yet. |
NVLink is not publicly unlocked on the CMP 170HX, on either card. It is fused off and also missing board components. The 8 GB card has no NVLink path at all; the 10 GB card may be reachable with a hardware mod that is not public. Source: @lia_oc, 2026-10-22
What blocks it
- Fuse:
OPT_NVLINK_DISABLEreads0x2on the 10 GB probe; CUTE measured the connector
pins on 8 cards (all populated, pins connected to the core) and believes NVLink is blocked by GPU fuses. Source: @cute_sc2, 2026-10-05
Source: @cute_sc2, 2026-10-05
- Missing microcode: GA100 has three on-die MINION microcontrollers for link training; the 170HX VBIOS lacks the
bootstrap image. The VBIOS is not cryptographically signed, so injecting the image is the plan, but it is not done.
- Missing board parts: someone counted 5 resistors present on the A100 PCB that are absent on the 170HX, plus 3
terminations; the expected failure mode of unterminated NVLink is inability to train. Source: @_orrorin, 2026-10-12 The 3.3 V NVLink clock generator parts are also missing; kater found U11 (the bridge clock generator, GS7612S5MA-R, on the back of the PCB near the IO shield) is unpopulated, so the bridge clock never comes up. Source: @onemillionkates, 2026-10-05
Source: @_arcanum_, 2026-10-07
Source: @ghostinthedatacenter_87281, 2026-10-22
Status of the hardware mod
Big Ptoughneigh: "it works fine, but requires a very simple hardware mod (easier than the x16 mod). It's not my finding
to share though." GhostInTheDatacenter has about 75% of the NVLink circuit components and is waiting on 50 milliohm
resistors plus parts to re-enable the power stages; if it works he will document a BOM.
Source: @bigptoughneigh, 2026-10-23
Source: @ghostinthedatacenter_87281, 2026-10-24
Source: @ghostinthedatacenter_87281, 2026-10-25
OB88594's advice for the missing parts: add the components that are missing and follow the A100 layout.
Source: @ob88594, 2026-10-24
mrpandagod is working on the software side after the RIR unlock and says it looks like it will work; he rewrote the SEC2
payload for NVLink during experiments. Nothing public as of 2026-10-28.
Bridges (for when it works)
A100-class PCIe cards use 3 bridge slots; each bridge carries 4 NVLinks (200 GB/s per bridge, 600 GB/s per pair), so an
8-card rig would need 12 bridges. Compatible parts: PNY RTXA6000NVLINK-KIT (2-slot), PNY RTXA6000NVLINK3S-KIT (3-slot),
NVIDIA 900-53651-0000-000. Source: @djpandaman, 2026-10-06
Source: @djpandaman, 2026-10-06
Chinese clone bridges are on Alibaba for about $200; a Taobao supplier quoted RMB780 unbranded / RMB900 NVIDIA for the
dual-slot 900-53651-0000-000, bought via Superbuy; on xianyu about $120 each. US retail is 150+ USD plus tax.
Source: @djpandaman, 2026-10-07
Is it worth it?
Miséricorde: NVLink would help only diffusion workloads and would need higher power limits, so it would not change much
for LLM inference; for GLM 5.3 Flash in TP4 it might add roughly 20-25%.
Source: @wakeupmbrc1, 2026-10-18
Source: @wakeupmbrc1, 2026-10-27
Source: @wakeupmbrc1, 2026-10-27
Pairs only (TP2) on A100-class PCIe; combining more than two cards over bridges is unresolved.
Status
Theory: no public software or hardware unlock, only in-progress hardware experiments. The 8 GB card has no path.