Can I utilize one dual output 8 pin cable for a graphics card requiring two separate 8-pin power connectors?
Can I utilize one dual output 8 pin cable for a graphics card requiring two separate 8-pin power connectors?
Some graphics cards need two 8-pin power connectors. Certain PCIe power cables have dual output 8 (6+2) pin connectors. You can use one such cable to supply power from the PSU's 8-pin output to the graphics card's two 8-pin connectors, provided it is done safely and correctly.
High-quality power supplies work best when using distinct cables to minimize heat generation, particularly with high-demand components. Another concern is that generic PCIe cables aren't suitable even if they appear compatible—they lack standardized pin configurations from manufacturers, increasing the risk of electrical faults since connections may not match the plug's terminals. The cable you mentioned is specifically for Corsair AX; depending on your PSU model, you should purchase a cable tailored to your unit. If you lost or didn’t receive spare cables during assembly, it’s wise to choose a compatible one.
The information provided outlines specifications for PCIe GPU connectors. A single 8-pin PCIe GPU connector can supply up to 150W. At 12V, this translates to approximately 12.5A, distributed across three yellow wires at about 4.16A each. If using an 18AWG wire rated for 9.5A in free air, the second connector can handle up to 300W and 8.32A per wire, which could be seen as pushing limits since the standard rating for three close wires is only 7A.
I need to understand why a well-known firm such as Corsair would include two 8-way plugs in some of their PCIe cables, even though they doubted they could deliver up to 300W. It’s better to be cautious and use one 8-way (150W) and one 6-way (75W) plug on the cable for a total of 225W instead of trying to reach 300W.
As previously discussed, with an 18AWG wire gauge and a "free air" rating of 9.5A per wire, the power capacity comes to about 114W per wire, or roughly 342W across all three wires. Since GPUs are only rated for around 300W from two 8-way connectors, there’s still some extra capacity left.
However, if we consider a "bunched" setup with each wire rated at 7A on 18AWG (about 9.5A per wire), the maximum power the PCIe lead can handle becomes 252W. If the GPU draws more than that from two 8-way connectors—excluding the motherboard’s 75W limit—there would be a significant shortfall.
In contrast, some high-power GPUs with older connectors are equipped with three 8-way power inputs for up to 450W, plus an additional 75W from the PCIe socket. For these models, using two 8-way plugs might not be necessary unless the GPU demands more than 252W.
It’s worth noting that some premium GPUs with "traditional" connectors have three 8-way power inputs capable of delivering up to 450W, but this would require at least two or even three separate PCIe leads for safety.
There’s also a concern that certain high-power cards might fail due to connector issues similar to older 12VHPWR cables on demanding RTX4090 boards. Manufacturers have claimed these problems stem from improper cable alignment rather than the connectors themselves.
In summary, I would be comfortable using both 8-way plugs if I had a reliable power supply, but I wouldn’t trust a budget PSU under $30 for this purpose.
Regarding this, consult Corsair.
They specialize in their products.
Recent graphics cards may exhibit exceptionally high power consumption, which can harm cables.
Therefore, it is advised to connect two cables for graphics cards featuring two 8-pin ports.
This is supported by Seasonic's suggestion to rely solely on a single 8-way connector for each PCIe connection.
The description of using both as "Standard" seems to hint that the cable design may not fully meet expectations, which aligns with my view about the limitations of using bunched 18AWG cables rated for only 7A per wire, limiting power delivery to around 252W.
A brief review of Seasonic PSU advertisements suggests their PCIe leads typically feature just one 8-way connector at the GPU side. If this is the case, it’s a positive step.
I’m more accustomed to Corsair PSUs that include dual-headed 8-way connectors, which makes it easier for users to utilize both simultaneously rather than relying on separate leads.
Perhaps it falls to those who draft ATX PSU cable standards to balance cost and performance, as manufacturers likely aim to minimize expenses per connector pair. The RTX4090 issues with early 12VHPWR connectors are a clear example of what happens when standards fall short.
I’m considering adjusting my advice to match Seasonic’s approach: use both 8-way connectors only on double-headed PCIe cables if no alternative exists, except perhaps by purchasing another power supply. I currently have one GPU needing two 8-way connectors and rely on two separate cables.
Corsair incorporated both 18AWG and 16AWG in their older dual-6+2 ribbon cable design, with the latter being a more practical choice for the first plug and the former for the second plug on their later sleeved cables. It seems they made some improvements.