Temperature & Acoustical Testing / Power Consumption
For all temperature testing, the cards were placed on an open test bench with a single 120mm 1200RPM fan placed ~8” away from the heatsink. The ambient temperature was kept at a constant 22°C (+/- 0.5°C). If the ambient temperatures rose above 23°C at any time throughout the test, all benchmarking was stopped. For this test we use the 3DMark Batch Size test at its highest triangle count with 4xAA and 16xAF enabled and looped it for one hour to determine the peak load temperature as measured by GPU-Z.
For Idle tests, we let the system idle at the Windows 7 desktop for 15 minutes and recorded the peak temperature.
With an efficient 28nm core beating at its heart the HD 7970 posts some very good temperature numbers, especially when compared to the HD 6970. This should also allow for some reasonable overclocking headroom at near default fan speeds. However, these low temperatures do come at a price….
Yes, we have finally added decibel testing to our repertoire and this section will expand in future reviews. What you see below are the baseline idle dB(A) results attained for a relatively quiet open-case system (specs are in the Methodology section) sans GPU along with the attained results for each individual card in idle and load scenarios. The meter we use has been calibrated and is placed at seated ear-level exactly 12” away from the GPU’s fan. For the load scenarios, a loop of Unigine Heave 2.5 is used in order to generate a constant load on the GPU(s) over the course of 20 minutes.
AMD claims their larger fan with its upsized fins should provide a quieter gaming experience but we didn’t see any of that during testing. The HD 7970 quite loud when compared to the NVIDIA cards. Its fan doesn’t shriek like a gut shot banshee (a la HD 6990) but the noise it puts out will certainly be heard throughout its immediate vicinity and any adjoining rooms if your case doesn’t have some form of acoustical dampening.
Interestingly enough, the fan doesn’t go above 40% so it is completely possible that one our engineering sample’s thermal sensors is slightly buggy but after speaking to some of our colleagues, several are achieving the same results. On the flip side of that coin some others have reported a perfectly quiet computing experience. Take this as you may but from our perspective, additional testing will certainly have to be done on retail products.
System Power Consumption
For this test we hooked up our power supply to a UPM power meter that will log the power consumption of the whole system twice every second. In order to stress the GPU as much as possible we once again use the Batch Render test in 3DMark06 and let it run for 30 minutes to determine the peak power consumption while letting the card sit at a stable Windows desktop for 30 minutes to determine the peak idle power consumption. We have also included several other tests as well.
Please note that after extensive testing, we have found that simply plugging in a power meter to a wall outlet or UPS will NOT give you accurate power consumption numbers due to slight changes in the input voltage. Thus we use a Tripp-Lite 1800W line conditioner between the 120V outlet and the power meter.
While we were disappointed in the acoustical results, there’s no denying that AMD hit the nail on the head in the efficiency department. Not only was our HD 7970 far more efficient than the GTX 580 but its in-game performance was significantly better as well.
When compared against the HD 6970, we honestly had to rerun the tests several times to validate the results because at first, they looked to be a mistake. Here we had a graphics card that beat out the previous generation flagship by a good 40% across the board and yet it consumed less power. Something didn’t look right but after hours of testing, it seems our initial impressions held out. AMD claims the HD 7970 should consume about as much as the Cayman XT so we may have just received a low leakage core but nonetheless, kudos to the design team on this one.
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