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Observed clock speeds
To evaluate the clock speeds these cards can reach at the stock settings we chose, I fired up the 2016 reboot of Doom with all settings maxed at 4K. This title can run at high framerates while occupying large amounts of graphics memory, so it's a great stress test as well as a great game.

  GPU
base
clock
(MHz)
GPU
boost
clock
(MHz)
Memory
speed
(MT/s)
Doom
GPU
clock
(MHz)
Nvidia GTX 1080 Ti Founders Edition 1480 1582 11000 ~1733-1759
Aorus GTX 1080 Ti Xtreme Edition 11G
(gaming mode)
1607 1721 11232 ~1885-1911
Corsair Hydro GFX GTX 1080 Ti
(gaming mode)
1632 1746 11016 ~1898-1911

With its "gaming mode" clock profile and its radiator fan fixed at 1700 RPM, the Hydro GFX likes to hang out around 1911 MHz. It'll occasionally boost up to 1923.5 MHz, and it can sometimes dip to 1898 MHz. A clock speed bin up or down now and then is fine performance. The clock-speed range of the Aorus GTX 1080 Ti is about a bin behind by my observations. That card settled around 1898 MHz as its midpoint, and it occasionally dipped to 1885 MHz and boosted to 1911 MHz. To be clear, the real-world performance of these cards shouldn't be noticeably different. Varying workloads and swings in ambient temperature will likely have greater effects on performance than one custom cooler or another will at stock speeds for the GTX 1080 Ti.

Nvidia's Founders Edition GTX 1080 Ti delivers lower boost clocks than either of these custom-cooled cards, but that's because of its strictly dual-slot cooler and 84° C thermal limit. I observed boost speeds ranging from about 1733 MHz to 1759 MHz once the card hit that limit. Even so, those speeds are well in excess of Nvidia's rated 1582 MHz boost clock. Both the Hydro GFX and Aorus Xtreme Edition 11G should be slightly faster in real-world use than the Founders Edition, but again, we're only talking a few frames per second more on average.

Overclocking
It's good to know how these graphics cards perform at stock speeds, but we don't imagine many builders buy hulking custom-cooled GTX 1080 Tis to run them at stock clocks only. To turn up the heat on this trio, we turned to MSI's Afterburner app. We first maxed out the power limit and temperature limit for each card before gradually increasing the core clock and memory offsets in Afterburner. We stopped when we saw signs of instability or crashing when we ran our Doom load.

  GPU
clock
offset
(MHz)
Memory
speed
(MT/s)
Doom
GPU
voltage
Doom
GPU
clock
(MHz)
Doom
GPU
temp. (°C)
Nvidia GTX 1080 Ti Founders Edition (OC) +190 12133 1.025V 1987 85
GTX 1080 Ti Xtreme Edition 11G (OC) +8 12133 1.043V 1974 72
Hydro GFX GTX 1080 Ti (OC) +122 12133 1.062 2050 55

I look at these numbers in a couple of ways. On the one hand, it's impressive that putting the GP102 GPU under water let me eke out a sustained 2050 MHz boost clock from the Hydro GFX. The GTX 1080 Ti Founders Edition tops out at 1987 MHz, and the Aorus XE 11G hits 1974 MHz. Thing is, for all its fancy cooling hardware, the Hydro GFX is only running about 3.1% to 3.5% faster than its air-cooled competition, and the differences in delivered performance between these cards is likely to be even narrower still—certainly narrow enough that one likely wouldn't notice any difference between them in real-world use. Even so, Corsair can claim the highest overclocked speeds we've seen from a GTX 1080 Ti thus far, and a close victory is still a victory.

In an improvement that may be a result of more mature drivers, both the GTX 1080 Ti Founders Edition and the Hydro GFX had no trouble maintaining both their core and memory overclocks when I pushed them to the limit this time around. Seems my concerns about the power-delivery circuitry on the Hydro GFX were unfounded.

GPU temperatures

If the Hydro GFX has one ace up its sleeve compared to the air-cooled GTX 1080 Ti competition, it's in GPU temperatures under load. At stock speeds, the Corsair card opens a whopping 17° C gap on even the massive Aorus cooler, and it completely freezes out the Founders Edition card with a 32° C advantage. Overclock the cards, and the Hydro GFX still maintains a 17° C gap on the Aorus and a 30° C gap on the Founders Edition.

While this huge temperature drop versus air coolers is the most impressive feature of the Hydro GFX, it sadly doesn't have much real-world use for Pascal-powered graphics cards. Nvidia locked down voltage tweaking for these cards, and that restriction remains in place on the GTX 1080 Ti. If I had even a small range of additional voltage to play with on this card, I might be able to push it to truly impressive extremes. As matters stand, it's hard to justify the Hydro GFX for its cooling performance alone. The cooler shouldn't stand in the way of extracting the most performance from a given GP102 chip, at least. It should also allow the Hydro GFX to hang at or near its maximum boost clock for the majority of the time under load.

Noise levels
While it's fun to see how far we can push the core clocks of various GTX 1080 Tis, cooling performance and noise production are where custom-cooled graphics cards really set themselves apart these days. To test noise levels, I used the Faber Acoustical SoundMeter app running on my iPhone 6S Plus. I positioned the phone 18" from each graphics card on an open test bench.


At idle, both the Founders Edition and the Xtreme Edition 11G card are noticeably quieter than the Hydro GFX. The Founders Edition card has its variable-speed blower to thank for the victory, while the Aorus card can stop its fans entirely at idle. That's not to say the Hydro GFX couldn't run with these two if we hooked it up to a fan controller, but we wanted to test how loud these cards get stock-for-stock. Using Corsair's installation instructions, the Hydro GFX isn't loud at idle in absolute terms, but it's definitely more noticeable than the competition thanks to its fixed fan speed.

If you do decide to hook up a Commander Pro to the Hydro GFX or manually slow the ML120 fan at idle, the rather coarse-sounding pump of the H55 all-in-one cooler will be the ultimate noise floor for the card at about 34.2 dBA on our test bench. Again, not loud, but not silent, either. The wide PWM range (500 RPM to 2600 RPM) of the ML120 does let us practically silence the 120-mm spinner at idle with the right tools, though.

Under load, the centrifugal blower on the Hydro GFX spins up alongside the ML120 fan, so the card's total noise levels creep up just a bit compared to its idle numbers. The Aorus card remains the quietest of the bunch. The Founders Edition has to work quite a bit harder to keep its GPU cool, so it's the loudest of these three by far.

Those standings hold when we consider overclocked noise levels, as well. The Hydro GFX spins up its blower ever so slightly more when we put the spurs in it, so it gets slightly noisier than the Aorus card. It's worth remembering that the Corsair card is running slightly faster than the Aorus, though. Despite its midpack overclocking result, the Founders Edition starts to toe the threshold of tolerability when we take noise levels into account at just under 50 dBA.

Absolute noise levels are only one part of the picture, of course. The character of a sound can make or break a heatsink, too. Corsair's ML120 fan deserves high praise for its noise character. At 1700 RPM, it produces a broad-spectrum and slightly high-midrange whoosh that sounds like air moving for the most part. It's by far the best Corsair fan I've ever laid ears on, and it's a fine match for the Hydro GFX's first-place overclocking performance. The ML120 isn't the only fan going on the Hydro GFX, though, and the card's centrifugal blower can make a slight high-pitched hiss when it's really turning. This hiss is barely noticeable, though.

How troublesome a noise is will always be a matter of personal preference, though, and I still have to give the edge to the Aorus card's massive air cooler here. Its three 100-mm fans aren't that much smaller than Corsair's single 120-mm unit, and they produce a much lower-pitched sound that's easier to tune out than the combination of the whoosh from the Hydro GFX's ML120 fan and the mild hiss of its blower. Neither card qualifies as offensive to my ear, but the Hydro GFX will always make itself known at the settings we chose to test it with compared to the Aorus' low-pitched sound.

Power consumption
To see how much juice these three cards are sucking down, we ran a spot-check with our Doom load and our trusty Watts Up meter. We measured total system power draw for our test rig minus its monitor, which was plugged into a separate outlet.


At idle, these three GTX 1080 Tis behave about identically, as we'd expect. Under stock load, the cards are within a few watts of each other, as well; that's a feather in the cap for the Aorus and the Hydro GFX since they're boosting higher than the Founders Edition card. Overclocked, the cards remain pretty closely matched. The Hydro GFX delivers its world-beating speed without making our test system draw a ton more power than the overclocked Founders Edition card does, and it lets our rig consume a bit less power than the Aorus card draws. On the whole, though, a GTX 1080 Ti is basically a GTX 1080 Ti when measured at the wall socket. This trio of cards has a basically identical impact on our test system's power draw.