Help with 8 pin GPU connections

[mardon85]

I've got quite a small SFX case (Ncase M1) and an SF750 psu. It's got x2 double 6+2 8Pin connections. 

Am I best connecting two individual cables from the Psu to a 2080ti or just use one of the double connectors? Space is tight so if two individual cables are better I'll order some shorter custom ones. 

[lafrente]

2080ti requires some power. I'd use 2 seperate cables unless PSU is really high end.

[mardon85]

Corsair SF750 is the best SFX PSU you can get but I have no idea if it can keep up with a full size one. 

The Gigabyte Gaming OC which is on the way apparently has LED's by the Pcie connectors which will flash if the the supply is unstable so I guess I could try both. 

[GoldenLag]

You can use one cable, or you can use 2. 

 

Theoretically there is a difference. Practically its not really. 

[seon123]

The 2080 Ti is a 250W card, so I'd recommend using two separate cables. For GPUs with a TDP above 225W, use two separate cables. 

[GoldenLag]

5 minutes ago, seon123 said:

The 2080 Ti is a 250W card, so I'd recommend using two separate cables. For GPUs with a TDP above 225W, use two separate cables. 

There is enough powerheadroom on a single double 6+2 pin to not worry about. 

 

As that should per spec do 150w each at 300w total with no issues

 

Then there is the extra 75w from the PCIe slot. 

 

So at least per spec there isnt an issue (not that there havent been issues before)

[seon123]

18 minutes ago, GoldenLag said:

There is enough powerheadroom on a single double 6+2 pin to not worry about. 

 

As that should per spec do 150w each at 300w total with no issues

 

Then there is the extra 75w from the PCIe slot. 

 

So at least per spec there isnt an issue (not that there havent been issues before)

The connector on the PSU side is still an 8 pin. On both Seasonic and Silverstone's websites, you'll find that they recommend two separate cables for GPUs >225W, iirc. 

[Sir0Tek]

27 minutes ago, GoldenLag said:

There is enough powerheadroom on a single double 6+2 pin to not worry about. 

 

As that should per spec do 150w each at 300w total with no issues

 

Then there is the extra 75w from the PCIe slot. 

 

So at least per spec there isnt an issue (not that there havent been issues before)

 

The problem is not that one cable can't deliver enough current, the problem will be that the high current provided by a single cable may heat up/overheat the cable itself.

[Juular]

Yeah, it's single-rail PSU, from power delivery side of things it doesn't matter if it's connected through one or two cables\connectors, but when such current are going only through one cable\connector it becomes a bit concerning, i vote for two cables too.

[GoldenLag]

50 minutes ago, seon123 said:

The connector on the PSU side is still an 8 pin. On both Seasonic and Silverstone's websites, you'll find that they recommend two separate cables for GPUs >225W, iirc. 

indeed they do. still, im just saying that the spec says it shouldnt be an issue. 

 

48 minutes ago, Sir0Tek said:

 

The problem is not that one cable can't deliver enough current, the problem will be that the high current provided by a single cable may heat up/overheat the cable itself.

then that would be an issue with the cable not being able to handle spec, wouldnt it. 

 

i am aware of cable burnthrough on high current singlerail PSUs, where it has happened that the current throughput is way higher than spec. 

[mardon85]

Thanks for all the replies everyone. 

Good point regarding the heat over time through the cable. 

I'll go with one for now so I can fit it all in and am awaiting a response to an email regarding custom ones. 

I'm hoping 25/30cm should be long enough without too much left over. 

Unless anyone has seen any already made up for sale in the UK that aren't £20 a go! 

[Sir0Tek]

1 hour ago, GoldenLag said:

indeed they do. still, im just saying that the spec says it shouldnt be an issue. 

 

then that would be an issue with the cable not being able to handle spec, wouldnt it. 

 

i am aware of cable burnthrough on high current singlerail PSUs, where it has happened that the current throughput is way higher than spec. 

It usually isn't a problem unless someone does use a single cable for a crossfire 2x Radeon rx 580 oc'ed setup, or similar. On the other hand, there's no harm to take the safe route.

[GoldenLag]

36 minutes ago, Sir0Tek said:

I usually isn't a problem unless someone does use a single cable for a crossfire 2x Radeon rx 580 oc'ed setup, or similar. On the other hand, there's no harm to take the safe route.

well this time its about ordering custom cables if needed.

2 hours ago, mardon85 said:

Space is tight so if two individual cables are better I'll order some shorter custom ones. 

as seen here

 

45 minutes ago, mardon85 said:

Good point regarding the heat over time through the cable. 

its not heat over time, its more about sudden inrush of current which burns the connector. at least when it comes to your PSU