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Sufficient amps/wattage for new video card and components?

Last response: in Components
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November 16, 2009 12:51:15 PM

Hey guys, first time poster here. I've been going insane trying to find a straight answer to a question I've had for the last few days. I'm sure this one has been asked about a million times already so my apologies in advance.

I just bought an XFX Radeon 4770 and I'm wondering if my current PSU will be enough to power everything I have in my machine plus the new card without any issues. The card has not arrived yet and I wanted to be sure I was going to be okay before I threw it in.

I'm using this power supply at the moment: http://img137.imageshack.us/i/budgetpower3.jpg/.
I've heard that 400 watts is enough to power the card on a mid range system but you need at least 20-25 amps on the 12v rail. I have honestly not paid much attention to anything other than brand and wattage when it came to power supplies until recently when I began to rebuild my old AGP machine from the ground up. I have not had the money to upgrade the PSU yet so in looking for an answer to this question, I found I had no clue about the rail amps, what they power, and if I would have enough wattage/amps for the card on top of my current components.

Since I don't know what specs would all be needed to form an opinion on if my PSU is sufficient, I'll just list off the basics:
AMD Athlon 64 X2 5200 Brisbane w/stock HSF
Biostar TF720 A2+ Mobo
Corsair XMS2 2GB DDR2 in DC (2x 1gb)
WD Caviar Black 500GB sata II HDD
HP DVD740 IDE dvd-rw
Sound Blaster Audigy LS
Case fans: 1 regular 120mm, 2 LED 120mm, 1 LED 80mm

I don't know what all consumes power from the 12v rail so if I missed something I apologize. If someone would not mind enlightening me to that, I'd appreciate it.

Thanks in advance.
a c 248 ) Power supply
a b U Graphics card
November 16, 2009 1:42:32 PM

AMD recommends a 450 watt power supply with 20 to 25 amps on a 12 volt rail.

It is a recommendation. A lot will depend on your components, configuration, and use. The 4770 is an energy efficient video card that does not use very much power. However, the +12 volt rail powers a lot more than the video card. The +12 volt rail accounts for about 75% of power consumption.

You power supply isn't a high quality unit. Looking at the specs of your power supply, it appears you are a short on requirements. Coolermaster actually recommends at least a 500 watt power supply for the 4770. You'll probably be okay if you are not a gamer into serious overclocking.

For comparison purposes take a look at the Corsair CX400 power supply:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

It is a high quality psu with current (amps) rated at 30 amps on the 12 volt rail. There's a big difference between 19 amps and 30 amps on the 12 volt rail. My best advice is to start planning for a psu upgrade.


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November 16, 2009 5:43:02 PM

Thanks for the reply.

From what I gather from your post, it would be possible for me to use the card for gaming as long as I keep the card and my cpu clocks at stock? Or did I take that wrong and that is that asking for trouble? Just want to make sure as I do not want to risk losing any components if the PSU does go dead.

I plan on trying to get another PSU as soon as I have the extra money, but I'd like to be able to use the card in the meantime. Is there anything that runs on the 12v rail I could potentially take out of my system or tweak the power consumption of to make the card safe to use?
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a c 277 ) Power supply
a c 196 U Graphics card
November 16, 2009 5:53:40 PM

Most components these days are powered by the 12 volt rail which is why ATX 2.x PSU's have the majority of their power on their 12 volt rails.

Using the PSU calculator
http://extreme.outervision.com/PSUEngine
and plugging in all of your specs, with 0% capacitor aging it expects 203 watts of power to be drawn by the system at 90% load, your PSU only has 228 watts of 12 volt power available, its going to be tight and you may get random shut downs while gaming. definitely invest in a new PSU soon, a corsair 400CX linked to above would be plenty for your needs and is only $40 after MIR.
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a c 248 ) Power supply
a b U Graphics card
November 16, 2009 6:18:35 PM

Hunter beat me to it.
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