The NVIDIA GeForce GTX 980 Review: Maxwell Mark 2
by Ryan Smith on September 18, 2014 10:30 PM ESTOverclocking GTX 980
One of GTX 750 Ti’s more remarkable features was its overclocking headroom. GM107 could overclock so well that upon initial release, NVIDIA did not program in enough overclocking headroom in their drivers to allow for many GTX 750 Ti cards to be overclocked to their true limits. This is a legacy we would be glad to see repeated for GTX 980, and is a legacy we are going to put to the test.
As with NVIDIA’s Kepler cards, NVIDIA’s Maxwell cards are subject to NVIDIA’s stringent power and voltage limitations. Overvolting is limited to NVIDIA’s built in overvoltage function, which isn’t so much a voltage control as it is the ability to unlock 1-2 more boost bins and their associated voltages. Meanwhile TDP controls are limited to whatever value NVIDIA believes is safe for that model card, which can vary depending on its GPU and its power delivery design.
For GTX 980 we have a 125% TDP limit, meanwhile we are able to overvolt by 1 boost bin to 1265MHz, which utilizes a voltage of 1.25v.
GeForce GTX 980 Overclocking | ||||
Stock | Overclocked | |||
Core Clock | 1126MHz | 1377MHz | ||
Boost Clock | 1216MHz | 1466MHz | ||
Max Boost Clock | 1265MHz | 1515MHz | ||
Memory Clock | 7GHz | 7.8GHz | ||
Max Voltage | 1.25v | 1.25v |
GTX 980 does not let us down, and like its lower end Maxwell 1 based counterpart the GTX 980 turns in an overclocking performance just short of absurd. Even without real voltage controls we were able to push another 250MHz (22%) out of our GM204 GPU, resulting in an overclocked base clock of 1377MHz and more amazingly an overclocked maximum boost clock of 1515MHz. That makes this the first NVIDIA card we have tested to surpass both 1.4GHz and 1.5GHz, all in one fell swoop.
This also leaves us wondering just how much farther GM204 could overclock if we were able to truly overvolt it. At 1.25v I’m not sure too much more voltage is good for the GPU in the long term – that’s already quite a bit of voltage for a TSMC 28nm process – but I suspect there is some untapped headroom left in the GPU at higher voltages.
Memory overclocking on the other hand doesn’t end up being quite as extreme, but we’ve known from the start that at 7GHz for the stock memory clock, we were already pushing the limits for GDDR5 and NVIDIA’s memory controllers. Still, we were able to work another 800MHz (11%) out of the memory subsystem, for a final memory clock of 7.8GHz.
Before we go to our full results, in light of GTX 980’s relatively narrow memory bus and NVIDIA’s color compression improvements, we quickly broke apart our core and memory overclock testing in order to test each separately. This is to see which overclock has more effect: the core overclock or the memory overclock. One would presume that the memory overclock is the more important given the narrow memory bus, but as it turns out that is not necessarily the case.
GeForce GTX 980 Overclocking Performance | |||||
Core (+22%) | Memroy (+11%) | Combined | |||
Metro: LL |
+15%
|
+4%
|
+20%
|
||
CoH2 |
+19%
|
+5%
|
+20%
|
||
Bioshock |
+9%
|
+4%
|
+15%
|
||
Battlefield 4 |
+10%
|
+6%
|
+17%
|
||
Crysis 3 |
+12%
|
+5%
|
+15%
|
||
TW: Rome 2 |
+16%
|
+7%
|
+20%
|
||
Thief |
+12%
|
+6%
|
+16%
|
While the core overclock is greater overall to begin with, what we’re also seeing is that the performance gains relative to the size of the overclock consistently favor the core overclock to the memory overclock. With a handful of exceptions our 11% memory overclock is netting us less than a 6% increase in performance. Meanwhile our 22% core overclock is netting us a 12% increase or more. This despite the fact that when it comes to core overclocking, the GTX 980 is TDP limited; in many of these games it could clock higher if the TDP budget was large enough to accommodate higher sustained clockspeeds.
Memory overclocking is still effective, and it’s clear that GTX 980 spends some of its time memory bandwidth bottlenecked (otherwise we wouldn’t be seeing even these performance gains), but it’s simply not as effective as core overclocking. And since we have more core headroom than memory headroom in the first place, it’s a double win for core overclocking.
To put it simply, the GTX 980 was already topping the charts. Now with overclocking it’s another 15-20% faster yet. With this overclock factored in the GTX 980 is routinely 2x faster than the GTX 680, if not slightly more.
But you do pay for the overclock when it comes to power consumption. NVIDIA allows you to increase the TDP by 25%, and to hit these performance numbers you are going to need every bit of that. So what was once a 165W card is now a 205W card.
Even though overclocking involves raising the temperature limit to 91C, NVIDIA's fan curve naturally tops out at 84C. So even in the case of overclocking the GTX 980 isn't going to reach temperatures higher than the mid-80s.
The noise penalty for overclocking is also pretty stiff. Since we're otherwise TDP limited, all of our workloads top out at 53.6dB, some 6.6dB higher than stock. In the big picture this means the overclocked GTX 980 is still in the middl of the pack, but it is noticably louder than before and louder than a few of NVIDIA's other cards. However interestingly enough it's no worse than the original stock GTX 680 at Crysis 3, and still better than said GTX 680 under FurMark. It's also still quieter than the stock Radeon R9 290X, not to mention the louder yet uber mode.
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Viewgamer - Friday, September 19, 2014 - link
To Ryan Smith. How can the GTX 980 possibly have a 165W TDP when it actually consumes 8 watts more than the 195W TDP GTX 680 !? please explain ? did Nvidia just play games with the figures to make them look more impressive ?ArmedandDangerous - Friday, September 19, 2014 - link
TDP =/= Power consumption although they are related. TDP is the amount of heat it will output.Carrier - Friday, September 19, 2014 - link
You're right, power consumption and heat output are related. That's because they're one and the same! What else could that electricity be converted to? Light? A massive magnetic field? Mechanical energy? (The fan, slightly, but the transistors aren't going anywhere.)Laststop311 - Friday, September 19, 2014 - link
no they aren't the same. Not all the electricity used is converted to heat. This is where the word EFFICIENCY comes into play. Yes it is related in a way but maxwell is more efficient with the electricity it draws using more of it and losing less of it to converted heat output. It's all in it's design.bernstein - Friday, September 19, 2014 - link
bullshit. since a gpu doesn't do chemical nor mechanical transformations all the energy used is converted to heat (by way of moving electrons around). efficiency in a gpu means how much energy is used for a fixed set of calculations (for example: flops)Senpuu - Friday, September 19, 2014 - link
It's okay to be ignorant, but not ignorant and belligerent.bebimbap - Friday, September 19, 2014 - link
there is "work" being done, as transistors have to "flip" by use of electrons. Even if you don't believe that "input energy =\= output heat" think of it this way100w incandescent bulb produces X amount of useful light
18w florescent bulb also produces X amount of useful light
in this sense the florescent bulb is much more efficient as it uses only 18w to produce the same light as the 100w incandescent. so if we say they produce the same amount of heat, then
100w florescent would produce ~5x the light of a 100w incandescent.
Laststop311 - Saturday, September 20, 2014 - link
ur so smart broGuspaz - Friday, September 19, 2014 - link
The power draw figures in this article are overall system power draw, not GPU power draw. Since the 980 offers significantly more performance than the 680, it's cranking out more frames, which causes the CPU to work harder to keep up. As as result, the CPU power draw increases, counteracting the benefits of lower GPU power draw.Carrier - Friday, September 19, 2014 - link
I don't think that can explain the whole difference. It performs similarly to a 780 Ti in Crysis 3, so the difference in power consumption can only come from the card. The 980 is rated 85W less in TDP but consumes only 68W less at the wall. The discrepancy gets worse when you add losses in the power supply.My guess is the TDP is rated at nominal clock rate, which is cheating a little because the card consistently runs much higher than nominal because of the boost.