Temperatures & 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.
The temperature results above don’t actually mean all that much due to a number of factors. Neither of these cards’ reference coolers will be featured on many retail boards since AMD’s partners have largely decided to eschew them in favor of custom setups. In addition, the HD 7850 we received will never be available with our sample’s heatsink design. With that being said, the results were very, very good in both cases.
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.
Once again, due to the fact that neither card will be widely available with the fans our samples came with, there really is much point in paying all that much attention to these results. We can however infer one thing from the low noise profiles of both cards: the Pitcairn core doesn’t produce all that much heat when operating at reference speeds so even a basic heatsink setup should be more than capable of handling it without resorting to loud high RPM fans.
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.
As with every one of the other HD 7000-series cards, the HD 7870 and HD 7850 set new benchmarks in the field of GPU efficiency. It really is amazing to see what AMD has been able to accomplish with the 28nm manufacturing process and hopefully this trend continues as new cards are released.
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