Power and Temperature Benchmarks
Power consumption is where the HD7900 excels and where AMD CPUs are supposed to excel. First off, we note that the HD7950 is setup to be a 225W card maximum – it only needs two 6-pin connectors ensuring compatibility with most gaming hardware made in the last five years. At idle the 7950 and 7970 should behave similar but at maximum load, the 7970 will draw more power
When we consider the CPUs, all three support the C6 power state, which allows for core slowdown and shutdown.
The AMD A6 APU has a 100W TDP however; we disabled the integrated graphics resulting in what can be estimated to be between 75-80 watts for the CPU and Integrated Northbridge alone. Idle speed is 800MHz
The 95-watt AMD FX-6100 system is at a slight power disadvantage, as its motherboard chipset is comprised of two chips whereas the AMD A6 and Intel i7 use a single piece chipset.
The FX series is set to idle at 1400MHz while The Intel i7 has a 130W TDP and idles at 1200MHz.
We also note that the Red system was using air cooling for the CPU while the green and blue used liquid cooling with only the front intake fan for the case enabled.
The large delta for our Intel Blue system is due to the two GeForce ‘Fermi’ GTX460 cards used versus our single HD7950OC graphics card.
GPU maximum Thermal Dissipation such as 150 W, 225W, 300W are typically set by their vendors using the most demanding application, which in recent years has been Furmark. NVIDIA has said on record it sets its GPU TDP using Furmark however AMD has not, despite this, many reviews use Furmark as do we.
We also ran Bitcoin mining overnight as a heat soak and stability test and GPU temperate did not rise above mid 60s
The reference HD7970 we previously tested ran hotter under load however, that has a different design cooler, more cores and higher clocks.
Zerocore was tested for correct functionality with both fans stopping when the 7950 entered long idle state.
