Question XfX 7900xtx speedster merc 310 triple 8 pin connection

[Gunnm123]

Would it be best to use three separate pcie cables or use a 3 way splitter? Does it even matter? Would there still be equal power delivery with either option?

 

[Aeacus]

Would there still be equal power delivery with either option?

7900 XTX is 355W GPU. PCI-E 8-pin power cable is rated for 150W. You WILL melt the PCI-E 8-pin power cable if you split it 3-way at the end, just to populate all 3x 8-pin PCI-E connectors on GPU. That, and no PSU is able to deliver all 355W through single PCI-E 8-pin cable.

Use three dedicated power cables to power the GPU.

 

[Tag1Oner]

Unless your PSU specifically says it can deliver 300W on each PCI-e cable coming out of the supply side, but it shipped with much heavier cables than most supplies I've used. If the PSU mfg. says it's ok you shouldn't have an issue splitting one of the cables to 2 on the card as long as you don't use some janky 3rd party splitter, but you'll still need another for the last power connector. If you have 3 cables and nothing else to do with them and free plugins on the PSU I'd just run them straight because I'm lazy. Unless you're on a threadripper or epyc you won't be plugging in another high draw video card anyway (lack of enough lanes and the motherboard probably doesn't have enough 8 pin CPU PWR connectors, so no point in saving the things in case you install something else... I've never seen anything but a GPU that required a 6 or 8 pin connector. The Superflower 1600W Ti I'm using allows from the supply on each port, and they sell an adapter that's one of the Gen 5 12VHPWR on one end and 2x 8-pin PSU on the other which I got rather than try to hang 4 connectors off my 4090 and find somewhere to tape them up so they weren't pulling on it.

Mine usually hovers around 3GHz boost and I didn't change anything there. I don't use it much anymore since getting the 4090, was hoping I could set it as the Houdini OpenCL card but it apparently has stupid problems when headless and silently crashes mid-compute. Will probably open the computer up to clean dust and take it out soon since I won't be getting that 5090 any time within the next decade; if I'm lucky I'll find another 4090 for MSRP while the scalpers and people who I'm pretty sure like to do things like pay over new sticker price for a used car if the dealer tells them it's hard to find work out the 5090s and $4000 payments for them amongst themselves.

 

[Aeacus]

Unless your PSU specifically says it can deliver 300W on each PCI-e cable coming out of the supply side

NONE of the PSUs say that. As i already said, PCI-E 8-pin power cable is rated for up to 150W by the PCI-SIG. And no PSU manufacturer can go past that.

I've never seen anything but a GPU that required a 6 or 8 pin connector.

Sure you have. Your fancy RTX 4090 has 12VHPWR connector on it and not the regular 6-pin or 8-pin PCI-E.

And RTX 30-series GPUs have the 12-pin PCI-E connector on them.

and they sell an adapter that's one of the Gen 5 12VHPWR on one end and 2x 8-pin PSU on the other which I got rather than try to hang 4 connectors off my 4090 and find somewhere to tape them up so they weren't pulling on it.

If you'd even want to hook 4x 8-pin PCI-E power cables to your RTX 4090, you can't. As i said, your GPU has 12VHPWR connector and it either needs 8-pin PCI-E to 12VHPWR adapter, OR when PSU is ATX 3.x, then PSU has dedicated cable that ends with 12VHPWR connector.

Btw, just using 2x 8-pin PCI-E to 12VHPWR adapter means that you've limited your GPU input power draw to 300W. So, your GPU will not operate at it's fullest.
RTX 4090 should have 4x 8-pin PCI-E to 12VHPWR adapter, so that power limit to GPU is 600W and one can use the GPU at it's fullest.

I don't use it much anymore since getting the 4090, was hoping I could set it as the Houdini OpenCL card but it apparently has stupid problems when headless and silently crashes mid-compute. Will probably open the computer up to clean dust and take it out soon since I won't be getting that 5090 any time within the next decade; if I'm lucky I'll find another 4090 for MSRP while the scalpers and people who I'm pretty sure like to do things like pay over new sticker price for a used car if the dealer tells them it's hard to find work out the 5090s and $4000 payments for them amongst themselves.

Care to tell how your problems help OP? 🙄

 

[ohio_buckeye]

Use 3 separate cables if you can, otherwise if use 2 with one spilt. My powercolor hellhound 7900 xtx for whatever reason only has 2 8 pin connections on it which is fine with me.

 

[Aeacus]

My powercolor hellhound 7900 xtx for whatever reason only has 2 8 pin connections on it

PCI-E 8-pin 150W + PCI-E 8-pin 150W + PCI-E x16 slot 75W = 375W, which is barely enough for 355W TDP GPU.

3x 8-pin PCI-E connectors on GPU would provide GPU better and more stable power.
Similar as where MoBos have 8-pin +12V EPS and also 2nd one just next to it. Most CPUs can work fine with just one EPS cable plugged in, but 2nd one is for additional stability in power delivery.

 

[Zerk2012]

The PCI SIG is way underrated.
Look at the cables that come with 2X6+2 pin connectors on one cable they still only have 3 +12v wires coming from the PSU connection.

 

[Aeacus]

The PCI SIG is way underrated.

Connector, wire gauge and wire insulation temperature rating actually define what kind of load entire cable can sustain.

E.g 16 AWG wire with 105C insulation temp rating can sustain up to 11A.
18 AWG wire with 105C insulation temp rating can sustain up to 10A.

But drop the insulation temp rating to 80C and you'd get;
16 AWG wire sustaining 10A
18 AWG wire sustaining 6A

PCI-E 6-pin and 8-pin plastic connectors with two circuits in it are rated for 9A per circuit. And when cable has three circuits in it, then 8A per circuit.

So, while the individual wire can sustain more (e.g 16 AWG with 105C insulation = 132W per wire or 396W with 3 circuits in it, e.g 8-pin PCI-E), the plastic connector in the end is actually the limiting factor. Since plastic connector can sustain 8A per circuit in 3 circuit configuration, making it ( 8x3x12= ) 288W.

Jargon aside;
6-pin PCI-E, 16 AWG, 105C insulation = 264W per cable
6-pin PCI-E, 16 AWG, 80C insulation = 240W per cable
6-pin PCI-E, 18 AWG, 105C insulation = 240W per cable
6-pin PCI-E, 18 AWG, 80C insulation = 144W per cable

8-pin PCI-E, 16 AWG, 105C insulation = 396W per cable
8-pin PCI-E, 16 AWG, 80C insulation = 360W per cable
8-pin PCI-E, 18 AWG, 105C insulation = 360W per cable
8-pin PCI-E, 18 AWG, 80C insulation = 216W per cable

6-pin PCI-E plastic connector (2 circuits in it) = 216W
8-pin PCI-E plastic connector (3 circuits in it) = 288W

While the cable itself can sustain more, the entire PCI-E power cable is held back by the plastic connector at the end of it.

But PCI-SIG has to play it safe and it has the ratings of;
6-pin PCI-E cable = 75W
8-pin PCI-E cable = 150W

Look at the cables that come with 2X6+2 pin connectors on one cable they still only have 3 +12v wires coming from the PSU connection.

Those PCI-E cables that have two 6-pin or two 8-pin connectors per cable, are still able to sustain what the plastic connector is rated for on the cable's end (namely on PSU side).

E.g plug in one of the 6-pin connectors and you can get up to 216W. Plug in both 6-pin connectors on the same cable, and you still get 216W combined between the two, since 216W is what the connector on PSU side is able to sustain. Push it more and the plastic connector melts. (Or when the wires are 18 AWG with 80C insulation, then wire insulation melts once the load surpasses 144W per cable.)