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Bofferbrauer on 18 December 2014
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cpg716 said:
vivster said:
sc94597 said:
vivster said:

re more than enough to have the system running at full power. You can take 550W to be on the safe side but more will be thrown out money and your PSU will run less efficent at idle performance.

Normally this is true, but the R9 280/280x/290 are very power-hungry. They can get as high as 280 Watts consumption. If his CPU wasn't also power-hungry he could likely get by with 500W, but his CPU has benchmarked to max at about 160W. That can be up to 420-440W usage for the CPU+ GPU alone. Considering that many of the average 500W rated PSU's really run around 450W, I wouldn't risk it. Heck, I have a Pentium G3258 (max watt consumption about 70 w) and an 280x, and was a bit worried that my 500W PSU wasn't enough. There are some good deals on 550W-600W PSU's though. I bought my 500W PSU for $40 and got a $20 rebate, which went to my Pokemon Alpha Sapphire purchase. The 600W version was only $15 more. 

Well I checked my sources before saying this. A whole system with overclocked 280X and a 4770k consumes about 350W. The 8350 consumes about 100W more than the i7. That's why 500W would be fine(if it is a good PSU it will deliver close to 500W) and 550W to be safe. Everything above that would be wasted unless he plans to overclock his CPU and get an overclocked 290X. I'm not used calculating with AMD.

My next system will be with an i7 and big Maxwell and I'm planning on getting a PSU around 400W and not bigger than 450W.

Most people go by the idea that you do DOUBLE your max CPU/GPU .. SO if its 350W.. You would want to do 700W+..      and I like I suggested..  going 750+ will allow him to Crossfire later on.. 

I generally calculate only 80% power output (the minimum efficiency requirement for an 80+ psu), and substract from them max TDP GPU, max TDP CPU, 50W for Mainboard and RAM, disc and hard drives and other things possibly connected.

Some hardware with a tendency to consume more than their TDP sells give them additional extra Watts, in this case 30W for the FX CPU and 20W for the 280 GPU, for a total of 50W extra power need. I generally also leave a bit headspace in case the psu deteriorates.

Here, we got 140W CPU, 180W GPU, 50W Bonus for their consumption behavior, and 50W for Mainboard, drives and others, for a grand total of 420W; and 450W with the aforementioned headspace. 80% out of 600W are 480W, so just above my headspace. 550W psu will work too (440W with 80% efficiency rule), but I wouldn't go down to or even below 500W for this particular configuration.

@Vivster: do you use 80+ gold or even platinum psu? Because if not, you're riding dangerously close to the limit with your projected i7/Big Maxwell configuration. A 450W psu might suffice, but I wouldn't take a 400W, even though it will probably work just fine. The reason it does so though is that low power psu are generally just regraded psu with more power output, and most of the time this is due to market demands, not limitations on the hardware itself. But if you happen to fall on such a psu some day, expect a lot of bluescreens due to failing power supply.