I am taking out all the raid drives, CD ROMs etc to clear as much space as possible for fans and ventilation, there will be only a USB stick. So most power will be for the motherboard and GPUs.
Good to know the rest of the systems general configuration, the amp ratings per voltage are still critical you can get 2 diffrent 500w power supplies and find out one of them is useless for mining because a majority of it's power is on the 3.3 and 5 volt rails and has an abysmal 12v load rating
This 480
http://www.newegg.com/Product/Product.aspx?Item=N82E16817170016although not a brand i would buy is a perfect example
+3.3V@28A, +5V@36A, +12V@16A,
[email protected],
[email protected],
[email protected]only 192 watts of meaningful power as far as mining is concerned, you couldnt run a 5830 on that if your CPU pulled more than 20 watts without damaging the PSU and potentially the rest of the system
This 500
http://www.newegg.com/Product/Product.aspx?Item=N82E16817139027Is a trusted brand and look at the diffrences
+3.3V@25A, +5V@20A, +12V@34A,
[email protected],
[email protected]408 watts now on the 12 volt rail if your cpu is rated for less than 100w you can easily fit two 5770 or a 58xx card plus a 5770 (three 5770 would be tight but possible and two 5830 would requre a low wattage cpu to be used but still tight but possible not that i reccoment either configuration)
Long post short the atx standard has changed some and if you're using existing power supplies they might not have the 12volt power you actually need
