A) How does the "590" there correspond to the actual power supply rating needed in a PC? Does this mean that you need a 600 W Power Supply minimum JUST for running the CPU and nothing else? (If so, then what's the point of the "125W" rating on the product specs??)
B) I have a 500W Power Supply, the Cooler Master eXtreme Power 500W (Model R-500-PCAR). Is this enough for running a Phenom II X4 955? (Along with one sata hard drive, one DVDRW, and a Radeon HD 3850.)
The above chart confused the hell out of me, so I'd like to learn more before purchasing a 955 (which I may do as early as tonight!).
Well, the original questions have already been answered. The top of the chart indicates measurements were taken at the AC source which means the power draw was measured at the electrical wall outlet. If go to the article's test set-up page you will see a list of components used for testing. The list includes power hungry graphics.
A high quality 500 - 550 watt power supply can power any single video card and overclocking. In some cases it might even be able to handle two video cards operating in dual mode. In your case a single HD Radeon 3850 video card uses about 73 watts and 6 amps at full load. From what I remember from yet another THG article your system will probably use about 300 watts at full load during a gaming session.
A few of the regular veterans at this forum use a meter that measures the power draw at the wall outlet. Some of the online vendors sell the meter for about $15.00 - $30.00. I think there is a Tom's hardware article or articles about individual AMD Phenom II cpu's that mention the cpu power consumption. I'm not sure about that.
The CPU isn't the main problem in deciding what PSU to get.The power hungry ones are the video cards. Overclocking CPU won't take that much hit on power requirements unlike when you include a graphics card to the system.
Is there any other way? Use a multimeter (if you know how to use one)
+1 what masterjaw said. That's why a lot of the threads in this section typically wind up being about psu requirements for video cards. It's not unusual to see a list of components where high end video cards operating in dual mode use a lot more power than the rest of the components combined.