RTX 5090 owner adds two 8-pin connectors to GPU with daughterboard mod dropping cable temps below 40C

An RTX 5090 owner has gone to great lengths to prevent any potential melting issues on their RTX 5090 graphics card by modifying the card with a daughterboard that puts the load of the 16-pin connector onto two additional 8-pin connectors on the board. Redditor DallasGrave published their mod on the PCMR subreddit, noting that temperatures on the wires of the 16-pin connector had improved significantly thanks to the mod and never broke 40C.

The mod consists of a single daughterboard with two 8-pin PCIe connectors attached to the backplate of the RTX 5090. To get these connectors to power the card, the bottom contacts of the 12V-2x6 connector are soldered to a pickup PCB that transfers power to the daughterboard. With this design, the power of the 16-pin connector is spread between itself and the two 8-pin PCIe connectors, essentially giving the card two extra 8-pin connectors to spread the load. The modder noted that with this setup, the power draw across all the wires and conductors was only around three amps, and at 550W full load for 48 hours, the wires never crossed the 40C mark.

This is a massive improvement compared to the operating temperature of some RTX 5090 graphics cards that have had their connectors melted. One of the worst cases involved Hardware Unboxed's ROG RTX 5090 Astral that melted, where the connector on their card reached a blisteringly hot 175C. The 8-pin mod is so good in the thermal department that it also operates below the operating temperature of normal 12V2x6 power connectors. The average operating temperature of the 12V-2x6 power connector is usually above the 40C range, with the connector's advertised temperature limit being 105C.

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What PSU cabling is needed to safely power the RTX 5090 mod’s two added 8-pin PCIe connectors?

The mod uses the card's 12V-2x6 connection plus two added 8-pin PCIe connectors on a daughterboard. The story does not specify what PSU cables to use for those two connectors or establish a safe cabling arrangement.

Could splitting power across two extra 8-pin connectors affect RTX 5090 performance or power delivery?

The mod spreads power across the RTX 5090's 16-pin connector and two added 8-pin connectors. The owner reported running the card at a 550W full load for 48 hours, with the wires staying below 40C, but no performance measurements were reported.

What electrical or warranty risks come with soldering a pickup PCB to an RTX 5090’s 12V-2x6 contacts?

Soldering the pickup PCB to the RTX 5090's 12V-2x6 contacts routes some power to two additional 8-pin connectors, but no specific electrical fault or warranty consequence is reported for this mod. The modder reported no wire temperatures above 40C during 48 hours at a 550W load; whether the modification remains reliable longer term is not established.

What other safeguards have been explored to reduce RTX 5090 12V-2x6 connector damage?

An ASRock TempGuard PSU was another attempted safeguard, but "Another RTX 5090 power connector melted, and even ASRock TempGuard failed to save this one" reports that it did not prevent a connector from melting. "Enthusiast attempts to install second 12V-2x6 connector on RTX 5090, is rewarded with a hole punched through the PCB" reports an attempt to add a second connector to reduce melting risk, but that modification failed.

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There have been many failed attempts to make safety guards for the 12VHPWR/12V-2x6 connector standard, so only time will tell if this mod will actually work. That said, this mod significantly improves operating temperatures, which is a leading cause of connector damage.