I'm not an expert in this area, KTE has so glad to give me an short crashcourse.
It's simple math i guess.
That corsair PSU has two 4pin rails (1 8pin if you prefer), on the M3A there is only a 4pin connector so you can only use one of those two.
I checked the specs and the three 12V rails all support 18A but all together only 40A (GBT Odin support 41A for all three).
With an board with just one 4pin connector you are in the same situation that I am with the M3A.
Assuming you run a phenom in a board with an 8pin connector you would not be limited by 18A but 36A. But then you would have only 4A left for the third 12V rail (pcie).
1.5V is too much for the phenom so ~20A is the max consumption you can expect for 12V1+12V2.
So in the worst case you whould have ~20A left for the 12V3. (240W).
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