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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  • medi01 - Monday, March 5, 2012 - link

    AMD released cards that are better than competitors in all areas: pricing, power consumption, performance, yet he found a way to be "dissapointed"

    You can't reason with fanboi.
  • Kiste - Monday, March 5, 2012 - link

    You're the one who seems obsessed with which company releases the "better cards".

    I'm merely commenting on the 78xx line of cards, which I find underwhelming in terms of price/performance ration - and I am not alone wiht this if you bothered reading the other comments here.

    So who's the fanboy?
  • formulav8 - Monday, March 5, 2012 - link

    You are. Your annoying as well.
  • chizow - Monday, March 5, 2012 - link

    Try laying off the personal attacks and focus on the arguments instead.

    I don't see how anyone can defend the pricing of AMD's 7 series stack in good conscience though, if roles were reversed and Nvidia were the one doing this, EVERYONE would be disappointed too I'm sure.
  • Kaboose - Monday, March 5, 2012 - link

    wasn't it everyone who said the 6000 series was too expensive back in october of 2010 and when Nvidia released the 500 series prices would come down a lot, then Nvidia released the 500 series right in between what AMD had and neither company really lowered prices for months. I think we will keep seeing more of that when the 600 series is released. This way BOTH companies profit.
  • chizow - Monday, March 5, 2012 - link

    Not sure what you're referring to, Nvidia launched GTX 570/580 before AMD launched the 6-series.

    And no Nvidia didn't raise prices on their 470/480 at the time which were at the same price points even though the 500 series extended that lead.

    AMD priced the 6000 series accordingly, and I don't recall anyone complaining other than being disappointed it didn't offer more performance.
  • SlyNine - Monday, March 5, 2012 - link

    5870 user here. What everyone defending the 7xxx node change doesn't consider that most of us dissopointed in SI are compairing it to other fab shrinks.
  • Iketh - Monday, March 5, 2012 - link

    You're on nvidia's payroll. Get off this site.
  • sseemaku - Monday, March 5, 2012 - link

    Are engineers in nvidia thinking in the same way and not releasing their cards! Good for AMD.
  • medi01 - Monday, March 5, 2012 - link

    7850 outperforms 570 while costing 80$ less.
    nFanboi much?

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