Ground is ground , right?...

[MYX]

Hey all, I am working on my cab. I have an extra PC power supply that I am using for miscelanious extra electrics. On the main 20 wire stack has many grounds. All grounds are ground right? I mean they had them lined up with +5v (red) Ground (black) color black color black... When building circuits ground is just ground and there is no ground for voltage a and ground for voltage b. Is this the case here?

While on the topic, the +12 v line that goes to the mother board (part of the 20 wire pack), does it supply the same amount of amperage, wattage?

asked differently...
Are each of the feeds (all the 5's, all the 12's, all the 3's) Are the outputs connected All the +12v lines feed off the same spicket?

what does power-ok do (Grey)

[MonMotha]

From a PC supply, all "Ground" wires are tied to earth ground inside the power supply (also implying that they're tied together).  You can safely return via any of them.  If you're tying into other power systems, be aware that not all power systems will tie power common and earth together (they'll have a floating common) and hooking the two together may give undesirable (read: sometimes really, really bad, but often not) results.

The 3.3, 5, -5, and -12 lines are also all commoned internally, and usually the 12V lines are commoned as well, though some (especially newer and higher end PC supplies) have two separate 12V rails for supplying hard drives (for the motors) and the motherboard electronics (onboard switcher for the CPU Vcore and sometimes a special connector for a video card) separately.  Usually this is advertised on the box.

As far as ratings, most supplies will have max ratings for each rail on the sticker on the side.  These are max ratings PER RAIL.  There's also a supply max rating across all rails that is the number the supply is sold as (or sometimes not - some supplies are crappy and rated as input power, not output).  Usually a note of any additional restrictions will also be made.  Often, these labels also include a handy dandy wire color guide.