GTX 970 Power from 2 modular cables?

[eXoTaylor]

I have the GTX 970 G1 Gaming. I heard that it requires a 28A 12v rail. The PSU I have shipping to me is the be quiet! Dark Power Pro 10. This PSU has 4 PCIe modular ports. 2 of which are 20 amp and the other 2 are 25 amp. Can I use one PCIe port 1 to connect one of the GPU power ports and PCIe port 2 to the other power port?

or option 2 is that this PSU has the ability to bridge the 4 rails into a single 12v @ 70A.

Which is the better option?


Thanks

 

[MeteorsRaining]

28A is for the system, not the GPU, the 970 is 150W TDP, meaning a mere 12.5A, and connecting the GPU to any one of the rails will suffice. Make sure it has a 6 pin and 8 pin in place. And you can't get 70A from 550W PSU btw.

 

[cowboydude99]

All GPUs should connect relatively the same.

Connect two cables from the PSU to the GPU. No need to bridge them.

 

[Murissokah]

Those requirements are really considering that you will be plugging more stuff on those rails. 20A at 12V provides 240VA, which should yield at least 200W (assuming a power factor of 0,83 or higher). Considering you will be using two rails for a single card with a 145 watt TDP, that requirement is largely overestimated and probably meant for SLI.

My opinion is that it will work with that PSU whatever way you set it up.

 

[Bitty]

This is what I found and the article by TH for the 970 and 980 seems to support this.

Got a Gigabyte G1 gtx970 (another later) to replace a very well-behaved AMD 9790 GHz. All seemed ok until I hit replay in Grid2 when it froze. Repeatedly it did this with oc or not but temps etc were fine. hmmmmm. Valley worked like a charm with none and big overclocks - no artifacts. Titanfall would freeze too. Asetto Corsa was fine. I looked about and saw a few complaining of similar issues thinking the 344.16 drivers were the cause. I suspected my psu might be an issue since other factors were okay and not everybody has the issue. I then found this article on power draw and the penny dropped.

I have an oldish Antec TP New Series 650 watt modular psu. I had the gtx970 on one 25A 12v rail feeding the 8+6 connectors. It seems this was possibly not enough to cope with the peaks. Not up on psus but with 80% efficiency that 25x12 is not a full 300 watts - more like 240watts. Whatever, I added another 12v rail for the 6pin and hey presto it worked fine no issue.

So anyone with such an issue might try this or get a more powerful psu.

 

[Murissokah]

Not up on psus but with 80% efficiency that 25x12 is not a full 300 watts - more like 240watts. Whatever, I added another 12v rail for the 6pin and hey presto it worked fine no issue.

This isn't really how efficiency is calculated. A 500 watt PSU should provide 500 watts no matter what. Efficiency will tell you how much power it draws from the outlet in order to do so. At 80% efficiency, a PSU would draw 625W from the outlet to deliver 500W to the computer.

What does matter to the calculation is the power factor. A 12v rail providing up to 25A would deliver 300VA (apparent power), which is not the same as 300W (active power). Active power is what is really needed, and that is a function of both the apparent power and the power factor (which in turn is a characteristic of the load, and not the source). So, if we assume the computer as a load has a 0.9 power factor, there would be 270W of power to be used.