RTX 4090 with disabled memory channel runs at 20GB, 48GB BIOS test also shown
© Paulo Gomes We received a tip from Jefferson Silva (Sidnelson) and Paulo Gomes, the Brazilian GPU repair team known for various memory mods, who claim to have restored two GeForce RTX 4090 cards with different faults.
According to the team, one MSI RTX 4090 suffered PCB damage that they link to bending or impact. To get the card working again, they used a modified BIOS that disables one memory channel . The result is a working RTX 4090 with 20GB of VRAM, down from the original 24GB. Cards that bend often suffer structural damage that disconnects memory modules or completely severs PCB traces, so this mod offered a quick way to recover a card that would otherwise be beyond repair. They add that the 20GB BIOS appeared recently and is already proving useful for GPU repairs.
Handle with care
This is also a good reminder to handle expensive GPUs carefully, especially models weighing more than 2kg. These small support brackets have been among the best-selling GPU accessories on Amazon for as long as I can remember. Many graphics card vendors now ship their cards with similar GPU supports, but if yours did not include one, it is worth spending a few dollars on one to help prevent sagging.
In the second part of the video, they also discuss a second BIOS test that makes the same class of card report 48GB of memory. NVIDIA has only ever listed the GeForce RTX 4090 with 24GB of GDDR6X, so this is not an official SKU. The repair team says the 48GB BIOS is meant for custom dual-rank PCBs, while their test board still had the normal single-rank 24GB layout.
Source: Paulo Gomes
Even so, the GPU reportedly initialized and output video with that BIOS, and monitoring software showed 48GB. The modders say that does not mean the board really has 48GB available. Their view is that the GPU does not fully validate total capacity during early initialization, and that workloads going past the physical 24GB on the board would likely lead to instability or a crash.
We have already covered real RTX 4090 48GB hardware mods before, but those relied on custom board work and added memory chips rather than BIOS behavior alone. So yes, I believe the BIOS is from our favorite Chinese AI firms that take gaming RTX 4090 cards apart and install such BIOSes.
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