Overclocking: Power, Temp, & Noise

In their marketing materials AMD is heavily pushing overclocking, and they have good reason to. With the 7970 we’ve established that Tahiti has quite a bit of overclocking headroom, and as the 7950 is clocked lower by default this opens up that headroom even further. Realistically AMD’s binning process means that the best clocking Tahiti GPUs are going to be allocated to the 7970 unless they have failed shaders, but even with that there’s quite a bit of potential on paper.

As with overclocking the 7970, our goal overclocking the 7950 is to see how much you can get for free; that is without any voltage adjustments. AMD’s reference PCBs are not particularly overbuilt for overclocking—cards like that will come later—so sticking to the reference voltage is the safest option, not to mention the easiest. With the 7970 we were able to get 200MHz (22%) overclocks without any voltage adjustment, and we’re hoping for the same out of the 7950.

With that said, we quickly ran into a wall on one card: the Sapphire 7950. Sapphire’s low VID of 0.993v may be great for temperature and noise at stock, but it’s not doing overclocking any favors. We only hit 950MHz at that voltage. As the Sapphire was the odd man out—every other card was at 1.093v—we did end up overvolting the Sapphire to 1.093v to see what it was capable of when put on similar footing as the rest of our cards.

After bringing up the voltage of our Sapphire card, all of our 7950s ended up overclocking to very similar levels. Our Sapphire and AMD cards topped out at 1025MHz core, a 225MHz (28%) overclock over a stock 7950 and a 125MHz (14%) overclock over the Sapphire’s factory overclock, while our XFX card reached 1050MHz, a 150MHz (17%) overclock beyond XFX’s factory overclock. Meanwhile the memory clocks on all of our cards topped out at 5.8GHz, beyond which we’d start seeing performance regressions from error correction on the memory bus.

Radeon HD 7950 Overclocking
  AMD Radeon HD 7950 Sapphire HD 7950 Overclock Edition XFX R7950 BEDD
Shipping Core Clock 800MHz 900MHz 900MHz
Shipping Memory Clock 5GHz 5GHz 5.5GHz
Shipping Voltage 1.093v 0.993v 1.093v
       
Overclock Core Clock 1025MHz 1025MHz 1050MHz
Overclock Memory Clock 5.8GHz 5.8GHz 5.8GHz
Overclock Voltage 1.093v 1.093v 1.093v

As you can imagine, with such similar overclocks, gaming performance on all 4 cards ended up being very similar. So we’ll get to gaming performance in a minute, while we’ll start with power, temperature, & noise.

Even though we’re not increasing the voltage on our AMD and XFX cards, merely overclocking them and raising the PowerTune limit to avoid throttling does drive the power consumption up. As is typical with heavily overclocked cards, overclocking quickly drives up power consumption and the 7950s are no exception. After overclocking power consumption is almost identical to the stock 7970, so while you can get 7970 performance you still need to pay the price with 7970 power consumption. Meanwhile it’s interesting to note that even with the extra 0.1v we’ve given the Sapphire card its final power consumption is only ever so slightly higher than the other 7950s, proving that voltage is the great equalizer in this case.

With the increase in power comes an increase in temperatures. The Sapphire card still does very well here staying in the low 70s even under OCCT, while the reference and XFX cards hit the high 70s under Metro and mid 80s under OCCT. As we’ve yet to really ascertain what the thermal limits are for Tahiti, it’s not clear whether there’s too much thermal headroom left for the GPU, particularly under OCCT.

Last but not least we have load noise. The Sapphire card is once more a stellar performer, and we still can’t get it above 50dB even with OCCT. Unfortunately the XFX 7950 BEDD has its biggest fallout yet—it may be able to overclock well, but at 64dB under OCCT the performance isn’t going to be worth the immense amount of noise it creates to move enough air to keep the GPU cool.

Power, Temperature, & Noise Overclocking: Game & Compute Performance
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  • chizow - Sunday, February 5, 2012 - link

    You want to talk about respect while throwing out inflammatory comments like fanboy every reply while ignoring the actual facts and logic of an argument? Respect is given where its due.

    Anyways, like I said, just draw out the pricing history on these high-end parts for the last 5-6 years and you will see what AMD is doing here is unprecedented. At no point has one of these GPU makers ever asked for flagship prices with so little improvement over the last-gen flagships when using a new process node/GPU architecture.

    If you are a reasonable person who is deserving of respect, I think you will find truth and reason in what I've written here, fanboyism and lack of respect aside.
    Reply
  • Galidou - Sunday, February 5, 2012 - link

    Find me anywhere I called you an idiot or a stupid or anything, the worse I said is that ultimate knowledge is crazyness, never called you crazy or ANYTHING, while you did it again., sad to see you have to resolve to those strategy as arguments....

    The lowest price I can find right now of the 7970 is 520$ and lowest I can find for 6950 is 240$, a little more than double as I said.

    I said I trolled and I know it inflammatory comments and lack of respect is different, I was poking your ''facts'' and the way you react and still lack of respect toward me just shows even more...

    ''who is deserving of respect''

    EVERYONE deserves respect and I will still respect you even if you don't for me because respect can't be bought, it is acquired or applied...
    Reply
  • Galidou - Sunday, February 5, 2012 - link

    And btw you still forgot to input the amount of memory which is 3gb that you forget everytime in your comments.... Reply
  • Galidou - Sunday, February 5, 2012 - link

    ''If you are a reasonable person who is deserving of respect''

    I just still can't beleive you said that... ''who is deserving respect'' it's deceiving to see such lack of respect in a conversation about gpus,

    I understand what you mean, Nvidia as always been about giving double the performance of last gen but they are hitting a wall where it won't be possible until they change the limit of the max TDP which is 300w, they are very close to it, I guess they left some space for double chip cards, but nvidia which isn't their strenght of watt/performance will probably have to change things if they want to squeeze double the gtx580 in their gtx680 in 300w TDP...

    Considering ATI are the best at watts/performance and they only squeezed that kind of performance in 250w.....
    Reply
  • chizow - Sunday, February 5, 2012 - link

    6950 was as cheap as $180-$200 in some sales and the 7970 is $550-$600, so yes at times it was 3x.

    But the point remains, the 7970 does a worst job at upholding your standard than the GTX 280.

    Also, it was a full 2x framebuffer, 8800GT was only 512MB, same as the 9800GX2 which was a massive amount of VRAM at the time. It was also more than the 512MB on the original 4870 with a full 512-bit bus.

    Once again, the 280 was a flagship card by every metric, if you want to argue honestly over the facts, at least try to be honest about it.
    Reply
  • Galidou - Sunday, February 5, 2012 - link

    Yes you're right the 8800gt was 512mb, wasn'T there a 1gb version? I can'T remember...
    4870 was cheating, it used the first ddr5 memory so it doubled the bandwidth without adding die size, which helped ALOT to it'S great performance, I still like my 4870 which can almost still run everything very well...
    Reply
  • Galidou - Sunday, February 5, 2012 - link

    ok you want to go in the ''as cheap as'' well my friend got right after me a rebate with special and had a 8800gt for 150$ after everything, I was using regular price for my 8800gt at 180$, so consider a 8800gt at 150$ times 4.33 = 650$, wow, 4 times and a third.... Reply
  • Galidou - Sunday, February 5, 2012 - link

    IT WAS A FLAGSHIP CARD LOL the radeon 4870 got so close to it with a die half as big and that was what, a month and a half later... speak about flagship at 650$ Reply
  • Galidou - Sunday, February 5, 2012 - link

    worse than that, the radeon 4870 wasn't even meant to compete with the high end, AMD had left that market for single GPU but still it came SO CLOSE... speak about Flagshipn amzingness that doubles the previous generation..... Reply
  • Galidou - Sunday, February 5, 2012 - link

    If you find something to say against my last comment I'm over with you, your closed mind will be the strognest I have ever seen. He will find a reason of the gtx 280 selling so high because of the Nvidia's CEO not having enough food on the table so they had to adjust the price....

    Poor them, send them food, they're starving!!
    Reply

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