Help: atx power supply

Hi guys, i'm building a i3 rework (trying to),so, in the long run i'm obviously buying and using a led strips power supply or a laptop charger (if that's a thing), but right now that i have only the electronics i was wondering if i could use this
[i.imgur.com]
[i.imgur.com]
as a power supply to get the electronics going while i buy the other parts, so in the end i'll only have to assemble everything.
Also, because i wanted to see if everything works.
The 12V rails as you can see add up to 20 A, so i should be fine, right ?
I have 5 nema 17, heated bed, limit switches, resistors, everything.
Thank you !

Edited 2 time(s). Last edit at 03/23/2016 01:55PM by Gibbon91.

You may need to put a load on the 5v and maybe the 3.3v to get the 12v to work properly.

Thanks for your answer.
Well i usually use it right away, but i never measured the current it generates, because my multimeter doesn't get that high ... but what does 12Vcpu means ? i'm thinking about getting everything to work, maybe even separately, first the motors and extruder then only the heatbed ....

The 12Vcpu could be the 12v supply on the atx connector for the CPU. Motherboards used to use the 12v supply for the cpu power regulators.