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How big of a power supply do you really need?

I'm building a cheap gaming rig for around $700, and I'm gonna be running a HIS Radeon HD 6850 and an AMD phenom x2 black edition 555 dual core that will unlock to 3-4 cores. What's the best way to determine how big of a power supply I need? Like I said I'm on a budget, and I'll downgrade the power supply wattage to downgrade the price :sol:
Is the amount of power needed by a power supply determined by the required wattage of the GFX card combined with the required wattage of the processor? Thanks
10 answers Last reply Best Answer
More about power supply need
  1. no more then 400 watts will be fine
  2. To satisfy yourself, use these calculators:

    http://educations.newegg.com/tool/psucalc/index.html
    http://www.corsair.com/learn_n_explore/

    To these calculated values, I would add about 20% for future expansion.
  3. How about this for 700$ -

    Asrock 870 Extreme3
    www.newegg.com/Product/Product.aspx?Item=N82E16813157198

    AMD Phenom II X4 955
    www.newegg.com/Product/Product.aspx?Item=N82E16819103808

    2 x 2GB DDR 1333 MHz RAM
    www.newegg.com/Product/Product.aspx?Item=N82E16820231275

    Radeon HD 6850 1GB Video Card
    www.m.newegg.com/Product/Product.aspx?Item=N82E16814150516

    Samsung SpinPoint F3 1TB Hard Drive
    www.newegg.com/Product/Product.aspx?Item=N82E16822152185

    Asus DVD Writer
    www.newegg.com/Product/Product.aspx?Item=N82E16827135204

    Antec 300 Illusion
    www.newegg.com/Product/Product.aspx?Item=N82E16811129066

    Antec 750W PSU
    www.newegg.com/Product/Product.aspx?Item=N82E16817371025
  4. How about this for 700$ -

    Asrock 870 Extreme3
    www.newegg.com/Product/Product.aspx?Item=N82E16813157198

    AMD Phenom II X4 955
    www.newegg.com/Product/Product.aspx?Item=N82E16819103808

    2 x 2GB DDR 1333 MHz RAM
    www.newegg.com/Product/Product.aspx?Item=N82E16820231275

    Radeon HD 6850 1GB Video Card
    www.m.newegg.com/Product/Product.aspx?Item=N82E16814150516

    Samsung SpinPoint F3 1TB Hard Drive
    www.newegg.com/Product/Product.aspx?Item=N82E16822152185

    Asus DVD Writer
    www.newegg.com/Product/Product.aspx?Item=N82E16827135204

    Antec 300 Illusion
    www.newegg.com/Product/Product.aspx?Item=N82E16811129066

    Antec 750W PSU
    www.newegg.com/Product/Product.aspx?Item=N82E16817371025
  5. Best answer
    gamerx456 said:
    I'm building a cheap gaming rig for around $700, and I'm gonna be running a HIS Radeon HD 6850 and an AMD phenom x2 black edition 555 dual core that will unlock to 3-4 cores. What's the best way to determine how big of a power supply I need? Like I said I'm on a budget, and I'll downgrade the power supply wattage to downgrade the price :sol:
    Is the amount of power needed by a power supply determined by the required wattage of the GFX card combined with the required wattage of the processor? Thanks


    1. plenty of people buy phenom II x2 to unlock and plenty of them come crying to this forum when they don't.
    2. benchmark reviews will often state how hungry a spec system with that video card will be during a stress test (non real world test) or gaming (real world). if your PSU can cover the stress test with a little head room then you are fine. luckily the AMD 6850 is very power efficient. see below. like obsidian stated a 400w PSU with most of its power on the 12v rail is plenty of power.
    CPU: Intel Core i7-920 @ 3.33GHz
    Motherboard: Asus Rampage II Extreme
    Chipset Drivers: Intel 9.1.1.1015 (Intel)
    Hard Disk: OCZ Summit (120GB)
    Memory: Patriot Viper DDR3-1333 3 x 2GB (7-7-7-20



    3. the amount of power needed is determined by all the hardware in the PC that require power.
    4. make sure you purchase a quality PSU and not just the cheapest 400-500w you see. currently the antec earthwatt models are on sale and the 500w unit has plenty of power for your build and future upgrades. its a fantastic deal @ $55
    http://www.newegg.com/Product/Product.aspx?Item=N82E16817371035&cm_re=antec_500-_-17-371-035-_-Product

    budget option at $35
    http://www.newegg.com/Product/Product.aspx?Item=N82E16817371033&cm_re=antec_380w-_-17-371-033-_-Product
  6. I'd recommend getting a 600W PSU simply because of your plans to unlock the 555. It will automatically want more power, and I feel that playing it safe with a higher wattage PSU would be a benefit for you. Plus the upgrade factor down the road.
  7. jockey said:
    I'd recommend getting a 600W PSU simply because of your plans to unlock the 555. It will automatically want more power, and I feel that playing it safe with a higher wattage PSU would be a benefit for you. Plus the upgrade factor down the road.


    your failure to understand CPU power is sad and funny at the same time. an unlocked phenom II will not need that much extra power, not even close (around 20-30w)

  8. This helped me out when trying to figure out how much juice I needed.

    http://extreme.outervision.com/psucalculatorlite.jsp
  9. Best answer selected by gamerx456.
  10. ct1615 said:
    1. plenty of people buy phenom II x2 to unlock and plenty of them come crying to this forum when they don't.
    2. benchmark reviews will often state how hungry a spec system with that video card will be during a stress test (non real world test) or gaming (real world). if your PSU can cover the stress test with a little head room then you are fine. luckily the AMD 6850 is very power efficient. see below. like obsidian stated a 400w PSU with most of its power on the 12v rail is plenty of power.
    CPU: Intel Core i7-920 @ 3.33GHz
    Motherboard: Asus Rampage II Extreme
    Chipset Drivers: Intel 9.1.1.1015 (Intel)
    Hard Disk: OCZ Summit (120GB)
    Memory: Patriot Viper DDR3-1333 3 x 2GB (7-7-7-20
    http://images.anandtech.com/graphs/graph3987/33245.png
    http://images.anandtech.com/graphs/graph3987/33246.png

    3. the amount of power needed is determined by all the hardware in the PC that require power.
    4. make sure you purchase a quality PSU and not just the cheapest 400-500w you see. currently the antec earthwatt models are on sale and the 500w unit has plenty of power for your build and future upgrades. its a fantastic deal @ $55
    http://www.newegg.com/Product/Product.aspx?Item=N82E16817371035&cm_re=antec_500-_-17-371-035-_-Product

    budget option at $35
    http://www.newegg.com/Product/Product.aspx?Item=N82E16817371033&cm_re=antec_380w-_-17-371-033-_-Product



    That benchmark testing really helped :)
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