Quote from: anodyne on June 12, 2011, 01:25:26 PM

Quote from: bcpokey on June 11, 2011, 09:37:30 PM

As usual everyone vastly over estimates needed power. Running a 4x5870 rig and a Kill-a-watt monitor I measured my rig to pull about 900Watts from the wall on a gold standard PSU, which means about 785Watts to the system.

So any quality 800 - 850Watt PSU will do you fine, just make sure you get something with either a single rail, or rails that can handle the amperage you draw for the GPUs.

I'm not overestimating, I'm making a recommendation. A little headroom gives extra protection from the downtime caused by having to do an RMA. And a good PSU can last a long time, so getting one that's has a couple hundred Watts extra might save you from buying another one if power requirements are different next year.

I agree with that.

Look at this article and the chart:
http://www.legitreviews.com/article/1080/13/

In "CrossFire", the HD 5870 system approaches 600W under full load. Keep in mind that the less GPU bottlenecked that the system is, the harder the CPU will work, thus increasing power consumption by the CPU. In simple terms, not all of the additional consumed power is going to the graphics card.

...
The difference in powerconsumption between "Crossfire" and a "Solo" graphiccard is about 250W.

So, 2 more 5870s in a rig at full load and overclocked you have to add about extra 500W to the 600W (Crossfire) shown in the article above. => 1100W => Therefore buy a 1200W PSU to be on the really safe side.