Trying to understanding PSUs

[Rlc]

Looking at these 2 models
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371054
http://www.newegg.com/Product/Product.aspx?Item=N82E16817182133



The rosewill provides 54A to a single 12v rail and the antec has 2 12v rails with 30A each.

So if using video cards with 1 6 pin pci-e connectors, then the antec should be better for a crossfire build even though it has 300 less total watts??

 

[ko888]

... the antec has 2 12v rails with 30A each.

No it doesn't. You don't add the two +12V rail amperages together because it doesn't work that way. The current limiter just limits the maximum current draw from each +12V rail to 30 Amps. If you're drawing 30 Amps from one of the +12V rail(s) then you can only draw 4 Amps from the remaining +12V rail.

Antec EarthWatts Platinum Series EA-450
• combined +12 Volt continuous current rating of 34 Amps
• two (6+2)-pin PCI Express supplementary power connectors

Rosewill HIVE Series HIVE-750
• combined +12 Volt continuous current rating of 54 Amps
• four (6+2)-pin PCI Express supplementary power connectors