Temperature & Acoustics / 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.
We’ve broken up the results for this section into the two different cards tested: one being the reference design while the other is the HIS version that comes with a custom heatsink.
Let’s get things started with the reference design which uses the same heatsink as the HD 7970 but attains lower temperatures courtesy of lower heat production from the Tahiti Pro core. It actually attains some of the lowest temperatures we’ve seen from a reference card in some time.
Moving on to the HIS design, we were rightly impressed by its results as well. Even though it doesn’t use an extensive (and expensive!) vapor chamber, the core temperatures stayed below those of the reference design.
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.
This is one area where the HD 7950 excels since the lower amount of core heat allows the reference heatsink’s fan to spin at a lower speed than on other Southern Islands cards. The result is a noticeably quieter acoustical profile than our HD 7970 and we can almost guarantee you that it won’t be heard above in-game sounds or even the other fans in your case.
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.
To say we were impressed by these results would be a massive understatement. Due to the highly efficient 28nm manufacturing process HD 7950 was able to post simply incredible power consumption numbers. With a max board power (which should hardly ever be attained unless the core is heavily overclocked) of just 200W, it undercut the GTX 580 by a significant margin and even left the GTX 570 eating its dust. For reference, this is about how much a HD 6950 1GB consumes at load and yet this card easily hits GTX 580 performance levels. Now that’s progress folks!
The HIS card meanwhile demonstrates how different cores can have different levels of power consumption since its numbers are slightly above those of the reference card despite slightly cooler temperatures.
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