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Overclocking: Power, Temp, & Noise

As with the rest of Southern Islands, AMD is making sure to promote the overclockability of their cards. And why not? So far we’ve seen every 7700 and 7900 card overclock by at least 12% on stock voltage, indicating there’s a surprising amount of headroom in these cards. The fact that performance has been scaling so well with overclocking only makes overclocking even more enticing. Who doesn’t want free performance?

So how does Pircairn and the 7800 series stack up compared to the 7700 and 7900 series when it comes to overclocking? Quite well actually; it easily lives up to the standards set by AMD’s previous Southern Islands cards.

Radeon HD 7800 Series Overclocking
  AMD Radeon HD 7870 AMD Radeon HD 7850
Shipping Core Clock 1000MHz 860MHz
Shipping Memory Clock 4.8GHz 4.8GHz
Shipping Voltage 1.219v 1.213v
     
Overclock Core Clock 1150MHz 1050MHz
Overclock Memory Clock 5.4GHz 5.4GHz
Overclock Voltage 1.219v 1.213v

Overall we were able to push our 7870 from 1000MHz to 1150MHz, representing a sizable 15% core overclock. This is now the 3rd SI card we’ve hit 1125MHz or 1150MHz – the other two being the 7970 and the 7770 – so AMD’s overclocking headroom has been extremely consistent for their upper tier cards.

As for memory overclocking, we hit 5.4GHz on both cards before general performance started to plateau, representing a 12.5% memory overclock. Considering that both cards use the same RAM on the same PCB, and the performance limitation is the memory bus itself, this is consistent with what we would have expected. With that said, we are a bit surprised that we got so far over 5GHz on 2Gb GDDR5 memory chips only rated for 5GHz in the first place; it indicates that Hynix’s GDDR5 production very mature.

With that said, because of the unique and non-retail nature of the 7850 AMD supplied us, the 7850 overclocking results should be considered low-confidence. The retail 7850 cards will be using simpler and no doubt cheaper coolers, PCBs, and VRMs; all of these can reduce the amount of overclocking headroom a card has. It’s by no means impossible that a 7850 could hit 1050MHz/5.4GHz, but it’s far more likely on a 7870 PCB than it is on a 7850 PCB.

Anyhow we’ll take a look at gaming performance in a moment, but in the meantime let’s take a look at what our overclocks do to power, temperature, and noise.

Even without a voltage increase overclocking does cause power consumption to go up, but not by a great deal. Under Metro the total difference is roughly 21W for the 7850 and 25W for the 7870, at least some of which can be traced back to the increased load on the CPU. Whereas on OCCT there’s a difference of nearly 40W on both cards, thanks to the increased PowerTune limits we’re using to avoid any kind of throttling when overclocked. All things considered with our overclocks power consumption for the 7850 approaches that of the 7870 and the 7870 approaches the GTX 560 Ti, which as we’ll see is a fairly small power consumption increase for the performance increase we’re getting.

Of course when power consumption goes up so does temperature. For both cards under Metro and for the 7870 under OCCT this amounts to a 5C increase, while the 7850 rises 8C under Metro. However as with our regular temperature readings we would not suggest putting too much consideration into the 7950 numbers since it’s using a non-retail design.

AMD’s conservative fan profiles mean that what are already somewhat loud cards get a bit louder, but in spite of what the earlier power draw differences would imply the increase in noise is rather limited. Paying particular attention to Metro 2033 here, the 7870 is just shy of 3dB louder at 51.9dB, while the 7850 increases by 2.7dB to 51.5dB. OCCT does end up being worse at 2.8dB and 3.7dB louder respectively, but keep in mind this is our pathological case with a much higher PowerTune limit.

Power, Temperature, & Noise Overclocking: Gaming & Compute Performance
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  • Galidou - Monday, March 05, 2012 - link

    Yep, this must be the best price/performance ratio the 7xxx series has to offer yet but still nothing worth of buying unless you got a 3 years old plus video card...

    7870 priced at 300$ I wouldn't mind changing my 6850 crossfire for one of those considering the wattage and temperature of my actual setup. I was considering a gtx580 as they can be found on ebay for around 400$ used but this 7870 is around the same in every game I play at the resolution I play them. Plus the 2gb memory and cheaper price tag for a new one...

    But I'll still wait for the price to drop or switch to kepler if price/performance is amazing... Heard it should be but it's all speculation on something that's not out yet...
    Reply
  • chizow - Tuesday, March 06, 2012 - link

    Only took 4th product launch from AMD for you to see what I was saying was true, but better late than never. ;)

    But yeah the real value right now is the last-gen parts going EOL and selling for extremely low prices. The 6950/6970s are mostly dried up in the channel, but there were GTX 480s for $219 last week, up next on the chopping block should be the 560Ti448/570/580 for great prices ahead of Kepler's launch.
    Reply
  • Galidou - Tuesday, March 06, 2012 - link

    I never said that you were totally wrong, I was only saying that it's not the worst thing that's ever happened in computer's history, while you were making a freaking case of it because I spoke against Nvidia...

    And you still can't name even an older radeon card in your short list of cheap video cards to get... At 130$ and 160$ for a radeon 6850 and 6870 respectively you still get ALOT for what you pay for. Radeon 6870 isn't far from gtx 560ti. Why mentioning it when you're being paid by the green goblin, they would stop sending your fanboy checks I guess, just teasing :P

    There's one thing extraordinary about this gen, the size plus wattage used for THAT kind of performance... is quite amazing, it should just be priced accordingly to it's die size and it would be dirt cheap LOL... but no bang for your bucks here...while in this segment of the market where you usually ''get it all'' about price/performance ratio. Lower the price of 50$ for every 7xxx video card and it will be ALOT better.
    Reply
  • BPB - Monday, March 05, 2012 - link

    If nothing else I gotta believe that the new nVidia cards will force a quick price adjustment from AMD. I think we'll see the AMD cards drop $25 to $50 when the nvidia cards come out. Reply
  • CeriseCogburn - Friday, March 09, 2012 - link

    After running blackbox 2.3 and wenning to the Turkish site I find something very interesting on Kepler:
    " Nvidia 's next-generation family of Kepler frequencies, dynamic graphics cards needed to improve their own work. Rumor has officially been confirmed as yet have the ability to dynamically overclock Kepler cards will leave a strong impact in the markets."
    --
    LOL - Dynamic Overclocking of Kepler similar to Intel turbo... very nice Nvidia...
    http://translate.google.com/translate?hl=en&sl...
    Reply
  • mak360 - Monday, March 05, 2012 - link

    "but $199 for a GTX 560 Ti is going to be hard to pass up while it lasts" I see you have to get a boot in there to AMD when possible. lol

    Most of the games are nvidia optimized where the 7850 loses one or two to the 560ti old tech.

    AMD`s been quite merciful to nvidia in regards to price points, when nvidia brings it on and the same happens (cards slot in without a challenge to AMD) I call shady business between the two or they don`t want to compete with each other, which is understandable i guess..

    Or maybe people need to forget the past and move on with "oh how nice and cheap prices were"
    Reply
  • sofreshsoclean2 - Monday, March 05, 2012 - link

    smoking card, faster than the 6970, fast as a gtx580 in a lot of those test but 150 smackeroos cheaper It is very close 7950 as well, finally a super fast card that is not 500 bucks. amazing card!! and nice review.

    thanks
    Reply
  • Devoteicon - Monday, March 05, 2012 - link

    Upgrade my overclocked 5850 for one of these? Thanks but no thanks. Reply
  • geniusloci - Monday, March 05, 2012 - link

    I'm going to be getting one or the other. I'll have to decide if the 7870 is worth the additional cash or not. They will most assuredly drop in price once Nvidia launches its product. Having come from a 560Ti this will feel something like a side grade in performance, but having found out how much better ATIs cards do 2D and video I simply can't return to the blurry mess which is Nvidia right now. Reply
  • Kiste - Monday, March 05, 2012 - link

    So it's 2012 and AMD gives us two cards that do little more than match the GTX 570 and 580 in price/performance.

    Southern Island has been a huge disappointment so far.
    Reply

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