Originally posted by: Beanie46
Originally posted by: Just learning
http://www.anandtech.com/video/showdoc.aspx?i=3520&p=11
According to this a Core i7 running @ 3.2 GHz and running two 260 GTX uses only 396 watts at full load. So maybe the power supply needs to be a little bigger than 450 watt (but not by much)
Unfortunately, what you've linked to is a stock speed system, an i7 965 cpu running at stock voltage and stock speeds, along with the video cards at stock voltages and speeds, completely ignoring the OP's "I'm going to overclock the cpu and gpu's..." comment.
OC'ing the i7 cpu requires increasing the core voltage and i7's use a LOT of power when overclocking, and generate a lot of heat, too.
This also doesn't take into account that two 260-216 cards running overvolted to OC them also adds to the ps output requirements.
Using the Extreme Outervision wattage requirement guesstimator, putting in an i7 920 OC'd to 4GHz on 1.3V (admittedly undervolted for such an ambitious overclock), 3 sticks of DDR3 RAM, two 260-216 video cards in SLI, two SATA hard drives, three 120mm fans, one PCI-e x1 card...for sound card, 90% system load gives a recommended PSU wattage of 602W. Not wholly unrealistic power requirements or system setup.
To think that an OC'd i7 with two OC'd 260-216 video cards would run smoothly on a 450W power supply is just beyond reason. Even if it did run, the power supply would be so close to running at 100% of rated output its life would be quite short indeed and would be at the worst end of efficiency, ripple and noise generation, and at the highest end of heat generation.
Honestly, trying to run his system with a small power supply, like a 450-500W unit, is just being penny-wise but pound-foolish. I cannot believe in this day and age people still advocate tying to save a couple of dollars on one of the most important pieces in a computer....the power supply.
Since power supplies are at their most efficient running at 50-60% of rated output, wouldn't it make sense to buy a little larger to get into that sweet spot of efficiency, not to mention having the ps run cooler, quieter, less stressed, and leave room for future expansion instead of running it at its ragged edge and have to replace it the next time the video cards are upgraded or cpu is upgraded?
Buy the Corsair 850TX.....it's not horribly expensive, has a solid +12V rail, good specs, has tested out very well on JonnyGuru, will run in the system you're building at under 60% of rated capacity, leave room for expansion, and not make you spend your money twice down the road.