Does my PSU Wattage really matter?

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Does my PSU Wattage really matter? Does size matter?

#1 Cactus John

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Posted 06 April 2011 - 01:47 PM

Background: I have been looking into upgrading a 5 year old pc of mine this week. Most new 512 video card recommend a power supply of 300-500 watts.

I cracked my case and found that i only have a 105 watt supply. When i pulled my old video card and ran the specs, it recommended a minimum of 300 watts. I have NEVER had an issue with my system internally.

QUESTION, does your power supply wattage REALLY matter when it comes to things like video cards? Please explain your answer in detail, YES NO is not answer, THANKS!

#2 90awdturbo

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Posted 06 April 2011 - 02:17 PM

It's not the wattage that really matters, that's more or less just a way to make power supplies look beefer. What you really need to look at is the Amperage on the 12v rail. That will be the rail that will be powering the video card.

You'll see some power supplies out there that claim to have 600 watts, but only 15amp on the 12V rail. Cheasy right? Keep an eye out for that crap(cheaper PSU's). I'd recommend looking into a Corsair PSU, there priced right and they've never done me wrong. I've also had good luck with OCZ.

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#3 dpunisher

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Posted 06 April 2011 - 03:39 PM

I just have to ask, "What desktop power supply is only rated at 105 watts?"

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#4 Cactus John

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Posted 06 April 2011 - 04:22 PM

dpunisher, on 06 April 2011 - 03:39 PM, said:

I just have to ask, "What desktop power supply is only rated at 105 watts?"

Shuttle - SUPER compact and a very small power supply

#5 Cactus John

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Posted 06 April 2011 - 04:26 PM

90awdturbo, on 06 April 2011 - 02:17 PM, said:

does it say that somewhere on the PSU sticker? i have no clue what a 12v rail is?

#6 killerx525

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Posted 06 April 2011 - 04:37 PM

Cactus John, on 06 April 2011 - 04:22 PM, said:

dpunisher, on 06 April 2011 - 03:39 PM, said:

I just have to ask, "What desktop power supply is only rated at 105 watts?"

Shuttle - SUPER compact and a very small power supply

Something is telling me that, the power supply is not standard ATX size.

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#7 Cactus John

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Posted 06 April 2011 - 05:37 PM

It is not the NORMAL PSU, its a LONG thin power supply, i would say normal PSU are square, this one is rectangle. I dont even know what classification this PSU is.

Edit:
Edited to remove unnecessary quote. ~ tg

#8 killerx525

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Posted 07 April 2011 - 01:51 AM

Probably a ITX size.

#9 90awdturbo

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Posted 07 April 2011 - 02:20 PM

There should be a sticker on the side or top of the PSU letting you know what each rail is rated at. Something in the mid 20's is pretty safe these days.

Make sure a new ATX PSU will fit however, like killer said i don't think your PSU is an ATX.

#10 killerx525

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Posted 07 April 2011 - 04:31 PM

The most wattage i've seen for ITX power supply is 300W on NewEgg.

#11 the_patriot11

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Posted 07 April 2011 - 04:35 PM

90awdturbo, on 06 April 2011 - 02:17 PM, said:

that is only a partially correct statement. Yes, the amperage on the +12 volt rails is important, very important, but the wattage is important to. You cannot get the amperage needed to run a modern video card without having that kind of wattage, you need to have both. The video card manufacturers put those requirements out there for a reason-because that is how much power is required to run that video card and the components of an average system. If you run even a modern low end card, with a min. 300 watt PSu requirement, on a 105 watt PSU, you will fry your PSU I don't care what amperage you have on your +12v rail, which on a 105 watt PSU, you will likely only have one.

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#12 Cactus John

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Posted 07 April 2011 - 06:11 PM

Okay, wow you guys have been a great help!

I am looking into getting a 300 watt Itx power supply, this SHOULD run a 512 AGP card w/o any issue and will fit my machine.

#13 90awdturbo

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Posted 07 April 2011 - 11:13 PM

the_patriot11, on 07 April 2011 - 04:35 PM, said:

90awdturbo, on 06 April 2011 - 02:17 PM, said:

Thanks for the correction

#14 killerx525

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Posted 08 April 2011 - 02:14 AM

Cactus John, on 07 April 2011 - 06:11 PM, said:

Okay, wow you guys have been a great help!

I am looking into getting a 300 watt Itx power supply, this SHOULD run a 512 AGP card w/o any issue and will fit my machine.

We need to be sure about this, what is the model of your desktop? Which AGP graphics card do you plan to fit in?

#15 Cactus John

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Posted 08 April 2011 - 08:23 PM

machine is a shuttle Xpc, It currently has a Gforce 6600 GT 128mb card. It is a MINI tower. There are a couple of card i would like to try to put in it, but i think i am going to stick with Ati Saphire 512mb or something to that nature, it was a 300 watt card, so it will work with the new supply