How big of a power supply do i need?

Sovea

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I have an ASUS Radeon HD 7770-2DG5 and I am trying to find out if my 400W PSU will run it and if I get a bigger PSU about a year down the road will it blow up my graphics card?
 
Depends on what 400W you have? How many amps does the 12V rails have? What is the rest of our build. 550W quality power supply is enough for most single gpu system. Getting a bigger power supply will not blow up your gpu.
Your system will draw the same amount of power from a 550W or a 1000W quality power supply. It doesn't actually supply 1000W to your system, it is just capable to up to 1000W roughly.
 

delellod123

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A psu wattage is just the max it can provide. A bigger PSU would not blow up any components, it will only have a larger POOL of juice for components to use. Your GPU only needs 110-130 watts under load. Depending on what else is in ur PC, you are probably fine with what you have. That being said, a crappy PSU, CAN blow up. Or just short out. In that case, the pc won't turn on and you will probably fry some components.
 

Sovea

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motherboard is an ASRock Socket AM3/AMD 890GX/Quad CrossFireX/ATX Extreme4 AND MY CPU is an AMD PHENOM II X4 940 BLACK AM2+ 3.0 GHZ and my PSU is an iMicro IM400W 400W ATX12V Power Supply
 

delellod123

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Are you using a the MOLEX connectors with adapters to power GPU?
If I were you, I would get a new PSU. The one you have may be rated for 400W, but in all reality, probably only provides about 60% of that.
 

Sovea

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but i heard that when you run a gpu on low power psu that when you get a bigger one it will kill it when it gets more power to the card ..... is that true or not?
 

delellod123

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Trying to think on an analogy. .. Think of PSU as a car engine. A bigger engine vs a smaller. Both can get you going 60 MPH, but only the bigger can get you going above 100. The little one just dosnt have enough power to do so. The car with bigger engine never gets harmed by going 30. That is the speed limit. But it alway has the potential to go faster.
 


A gas tank would be more appropriate than a car engine but it works...kinda.
Car engine is really an analogy for some gpu comparisons when talking about 60fps.
 

delellod123

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I thought of the gas tank, but then started to think about refueling. Although, the gas pump could have been the electrical socket. Hey, this was thought up on the fly while at work.... I guess rethinking, I would use that analogy for GPU or CPU.