GTX 970 Power from 2 modular cables?

eXoTaylor

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Sep 14, 2014
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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
 
Solution
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.
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.
 
Solution

Bitty

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Sep 16, 2006
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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.
 


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.