Hardware setup | Power consumption
Hardware installation
Installation of any of the AMD Radeon cards is really easy. Once the card is seated into the PC make sure you hook up the monitor and of course any external power connectors like 6 and/or 8-pin PEG power connectors. Preferably get yourself a power supply that has these PCIe PEG connectors native (converting them from a Molex Peripheral connector anno 2012 we feel is a no-go).
For the two cards, make sure you seat the card in the highest available PCIe slots (x8/x16), and bridge them with the crossfire connector. We've shown you that in a previous chapter in this article.
Once done, we boot into Windows, install the latest ATI Catalyst drivers and after a reboot all should be working. In the Catalyst Control Software make sure CrossfireX is enabled. No further configuration is required or needed unless you like to tweak the settings, for which you can open the Catalyst Control Center.
Power Consumption
Let's have a look at how much power draw we measure with this graphics card installed.
The methodology: We have a device constantly monitoring the power draw from the PC. We simply stress the GPU, not the processor. The before and after wattage will tell us roughly how much power a graphics card is consuming under load.
Note: For our power cunsumtions tests we no longer use FurMark as stress test. Furmark is very malicious on the GPU, so malicious that it does not represent an objective power draw compared to really hefty gaming. If we take a very-harsh-on-the-GPU gaming title, then measure power consumption and then compare the very same with Furmark, the power consumption can be 50 to 100W higher on a high-end graphics card solely because of FurMark.
We decided to move away from Furmark in early 2011 and are now using a game like application which stresses the GPU 100% yet is much more representable of power consumption and heat levels coming from the GPU. We however are not disclosing what application that is as we do not want AMD/ATI/NVIDIA to "optimize & monitor" our stress test whatsoever, for our objective reasons of course.
Our test system is based on a power hungry Core i7 965 / X58 system. This setup is overclocked to 3.75 GHz. Next to that we have energy saving functions disabled for this motherboard and processor (to ensure consistent benchmark results). On average we are using roughly 50 to 100 Watts more than a standard PC due to higher CPU clock settings, water-cooling, additional cold cathode lights etc.
We'll be calculating the GPU power consumption here, not the total PC power consumption.
Above, a chart of relative power consumption. Again the Wattage shown is the card with the GPU(s) stressed 100%, showing only the peak GPU power draw, not the power consumption of the entire PC and not the average gaming power consumption.
Here is Guru3D's power supply recommendation:
- Radeon HD 7950 - On your average system the card requires you to have a 500~550 Watt power supply unit.
- Radeon HD 7950 Crossfire x2 - On your average system the cards require you to have a 700 Watt power supply unit as minimum.
- Radeon HD 7950 Crossfire x3 - On your average system the cards require you to have a 850~900 Watt power supply unit as minimum.
If you are going to overclock GPU or processor, then we do recommend you purchase something with some more stamina.
There are many good PSUs out there, please do have a look at our many PSU reviews as we have loads of recommended PSUs for you to check out in there. What would happen if your PSU can't cope with the load:
- bad 3D performance
- crashing games
- spontaneous reset or imminent shutdown of the PC
- freezing during gameplay
- PSU overload can cause it to break down
Let's move to the next page where we'll look into GPU heat levels and noise levels coming from this graphics card.
