URGENT: Need help on picking a PSU

I am confused on what to look for when I plan to buy a PSU.

I understand wattage is a big requirement with higher end systems. Basically I am building upper middle - higher end computer for gaming.

Now, I dont have a super high end GPU yet, but I plan on buying one between middle-high end pretty soon.

So far I got an AMD AM3 MoBo with a 790x chipset, Athlon II X2 PRocessor which will be emulated to 4 core (3.1 hz). I got a crappy PCI-E ATI SAphire 3650 HD series GPU with 512MB DDR3 i believe. What else, lets see, well thats about the most important parts of my computer. The case I got has fantastic airflow and 6 fans capability.

Now, I need to know what I can get as cheap as possible. SO I believe from waht I read so far, that I am primarily looking for PSU's with high AMP outputs on the 12volt rail?

My first pick wouldve been: 800Watt PSU

However I swaw that it only provides a measly 20 Amperes through 4 12v Rails, I dont even know how the hell all the rails add to 800 because they clearly dont and I dont understand why they dont? (like wtf man? 12x20, multiplied by 4, is allraedy above 800)

So my second choice is a 650Watt SUpply which gives over 52 Amps. However it is only 650Watts and I dont know if thats going to be enought for a good card?

This is the case I decided to pick based on its functionality, space, airflow and price:
8 answers Last reply
More about urgent picking
  1. You can easily get by with a decent 500W PSU and still have room for a future video card upgrade.
    Right now with your un-locked 4 core Athlon II CPU and HD 3650 you could even get by with a nice 350W PSU.

    To figure the actual +12V amperage you'd need to know the maximum combined power available to the +12V lines. You get that off a PSU's data plate.

    In this example you see 12V1 and 12V2 are rated at 18Amps each. But the power supply note
    says "(+12V1 & +12V2 = 360watts Max)" So 360watts divided by 12volts = 30Amps.
  2. OCZ Stealth Xtream 500W PSU £46 would get the job done and allow a future video card upgrade to something like a HD 5770.
  3. Well, thnx for tjhe reply however a bit late. I have allready ordered a PSU for myself, according to calculations, it should have around 50 Amps on a 12V rack.


    It has 650 Watts and is reasonably prices, I am expecting this will cover most of my long term needs including a good gpu.

    What do you think, did I make the right choice?
  4. You could have spent less. But you got good value for the money you spent.
    That PSU will handle a future Crossfire setup of 2 5770s or even 2 5850s without a problem.
  5. And who knows, maybe CM has learned to build reliable PSU's with the GX line.
  6. The PSUs from the GX-series are decent units. Nothing more. The voltage regulation and noise supression are not good enough. Seventeam has some room for improvement.
    On the other hand, the PSUs from the Silent Pro M series are a better choice. Enhanced electronics has done a good job in the 500W, 600W and 700W models.
    The 850W and 1000W units have been made by FSP. Both are quality PSUs too. Anyway, I prefer the units from Enhanced.
  7. Hmm, thanks for the feedback.

    I guess I am not really into the whole testing and voltage stability thing. I understand the product I got is fairly well made. Not super, but its allright.

    So basically I bought the 650WAtt Coolermaster GX because of the single 12v Rail with 52 amps, which I believe is a really good deal since a lot of other PSU's in the same price range, INCLUDING the OCZ STealth Scout or w/e, had less than 20 amps on a 12 rail.

    Secondly because its 650 watts instead of 500 just incase I decide to go crossfire in the future, and who knows what kind of things ill be adding.

    Thirdly I might be doing some overclocking on an amateur level, say minor speed increases.

    As long as this product will allow me to say upgrade to a 5770 or a 5850 GPU, and allow it to run at maximum potential then I am happy.

    I was seriously considering the 500W OCZ PSU however was not impressed with the 18A 12 rails.
  8. alexander0884 said:
    Secondly because its 650 watts instead of 500 just incase I decide to go crossfire in the future, and who knows what kind of things ill be adding.

    Take in mind that 5850CF needs four 6-pin connectors. Your GX650 has only two (6+2)-pin connectors, so you will need an adapter to be able to run 5850CF, which is not recommended. On the other hand, your PSU is ready for 5770CF (two 6-pin connectors PSU recommended).

    Anyway, don't get me wrong. Your GX650 is not a bad PSU. I just think there are some better options.
Ask a new question

Read More

Power Supplies Components