New Graphics Card and PSU

Hey People!

Im new to upgrading computer stuff, so go easy please!

Well this is my current system:

Motherboard : Asus M4N68T - Pro
Processor : AMD Phenom II X4 955
Graphics Card : NVIDIA Geforce GT 240
Ram Memory : 4GB DDR3
PSU : ATX-500 (is what it says on the side of the thing)

The ATI HD 7850 has been reccomended. I was told to check the brand and the 12V rail to make sure I have enough power and a reliable PSU.

My psu doesnt seems to have a brand name at all. All it says is ATX - 500 (500W) switching mode power supply. underneath a loada colours with some numbers and letters.
Whats a 12V rail...how can I find it. And how do I knows its got a good supply?

In this list on the PSU there is a: (colour)(..of wire?) yellow - (DC) +12VDC - (Maximum Output) 22A
Theres also: (colour) blue - (DC) 0.5A - (Maximum Output) 0.5A
Is this what Im looking for? If so can you please tell me if this is enough for the graphics card in question?

Sources: CPUID program
http://www.videocardbenchmark.net/high_end_gpus.html

Thanks very much Very Happy

12 volt rails are sort of like circuits. Most PSUs only have one 12 volt rail, although there are some that have multiple. Each one is rated for a certain number of amps, much like a circuit in a house, and can only provide that number of amps to all of the devices on that rail. For example, it looks like your power supply has one rail that can provide a maximum of 22 amps. This means that all 12 volt devices (graphics cards, fans, hard drives, etc.) cannot collectively draw more than 22 amps at at time.

As for your specific graphics card, AMD's site says that the 7850 requires 75 watts to run properly. 75 watts / 12 volts = 6.25 amps. So, assuming your other 12 volt devices do not exceed 15.75 amps, the card should in theory work fine, and unless you have the least efficient equipment known to man, then you should not be coming close to that limit.

However, I would be careful of using that power supply. You say that there is no brand on it, meaning that it's probably some cheap one that the case manufacturer threw in. Those are a bit unreliable, and can break even if you aren't trying to pull too much power. Thus, while you should in theory be fine with your current PSU, I would personally buy a new one from a trusted company if you have the money.

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