7970 OC - PSU limited?

[Halogen23]

Recently I made the plunge and upgraded my graphics card to a 7970. I ended up reformatting windows and all seemed well as I was in benchmark heaven, exploiting the beast to my heart's content. Of course seeing how well the 7970's oc, I had to join the party

Most oc's I got were appearing to be stable under loops of 3dmark and MSI kombustor, but I realized something was wrong when I would get hard locks in games (BF3 & stalker COP especially) where the entire computer would lock down. I thought this was very strange as Win7 seems adept at handling the video driver's failure pretty well. So I dialed back the OC to more reasonable levels thinking it was the chip just being pushed too hard...

At work today it dawned on me. I haven't seen errors like this since before I knew to invest in a quality PSU. My overclock must be limited by it:hmm:

I used this tool http://extreme.outervision.com/psucalculatorlite.jsp to determine the total needed wattage output required to run my setup subsituting the 7970 for a 6970 and artificially inflating the wattage some to count for the difference in the two cards' consumption by raising my CPU OC numbers.

The results I got were a minimum required wattage of 581 and a recommended wattage of 631wD: at %100 system load. At %90 system load(closer to actual total power draw during gaming most likely) it was 523w and 573w respectively.

Now a few things come to mind:
1. DAMN.
2. DAAAAAAAAAAAMN.
3. I am Super Proud of my minibeast XFX PSU!
4. I am barely within the threshold of my psu's capability.


For reference purpose, this is a review of my PSU along with a retail listing:
http://www.newegg.com/Product/Product.aspx?Item=N82E16817207013
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story3&reid=225

Who here thinks I could get away with leaving things as they are? Who thinks otherwise and why?

 

[dma0991]

I would usually refer to Guru3D when it comes to knowing the bare minimum PSU required for a particular card and for yours it did say 550W for a single HD7970. I'm also assuming that you did not raise the voltages in the GPU yet and only increased the clocks which should increase the power consumption by a bit but not a whole lot that it exceeds 550W.

I've used the PSU calculator in the past but I often find the figures higher than it needs to be so I don't trust them anymore.

 

[Rvenger]

Did you put a killawatt to your computer to see how many watts you are drawing from the wall?

 

[gramboh]

I dunno what that CPU pulls, but I highly doubt you are running anywhere near 550W with a single 7970 without overvolting it a lot.

 

[Ovven]

Increase GPU voltage, and see if the computer still locks up at that OC.

 

[fffblackmage]

I doubt you're maxing out the PSU's power output.

If you really didn't have enough power... I'd think you'd have a BSOD or the rig would have shut itself off. The fact that only the video drivers crashed is a pretty good sign that your 7970's overclock is not stable.

 

[Halogen23]

Did you put a killawatt to your computer to see how many watts you are drawing from the wall?

This was a great idea! Im not sure why I didnt think of it.

Dug up the ol' kill-a-watt and plugged it up. After booting to windows, I fired up msi kombustor using the most demanding features of it and also loaded the processor fully with prime95. The highest I saw the wattage reach was 526w at the wall. This translates to much lower than I was led to believe by the wattage calculator.

I would usually refer to Guru3D when it comes to knowing the bare minimum PSU required for a particular card and for yours it did say 550W for a single HD7970. I'm also assuming that you did not raise the voltages in the GPU yet and only increased the clocks which should increase the power consumption by a bit but not a whole lot that it exceeds 550W.

I've used the PSU calculator in the past but I often find the figures higher than it needs to be so I don't trust them anymore.

I am beginning to see your point. My little experiment has confirmed your suspicions of inflated power requirements there.

I will do some testing with BF3 to see how things turn out. I will post results soon

 

[Halogen23]

Playing 64 player Caspian Border, I saw a max power draw of 398w. It seemed to average about 375. This seems to eliminate the possibility of me having a PSU limitation of overclocking my 7970 entirely.

 

[lehtv]

And this 398W was AC power? At 85% efficiency that'd be only 340W out of 550W or 62% out of rated wattage. Well within safe limits - the PSU is advertised as 550W continuous safe power.

 

[BFG10K]

As others have already said, it’s unlikely to be the PSU; more likely your card simply doesn’t overclock as well as you want it to, but then non-factory overclocking has never been guaranteed.