Is 400W enough for my future Graphics Card

[Kenter]

Hi, i'm planning to buy new graphics card, ASUS HD 7770. I read that it needs ~150W, but i have 400W PSU.
I have Motherboard: Asus M3N74-VM
3x 2GB DDR2 RAM
500GB SATA HDD
CD/DVD Rom.

Does my PSU run that card well?

Graphics Card site:ASUS - HD7770-2GD5
Motherboard site:ASUS - M3N78-VM


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Regards
-Kenter

 

[TVeblen]

Use a power supply calculator to determine the minimum output needed for the card and all your components;
eXtreme Power Supply Calculator

There are 2 schools of thought here: Just Enough - vs - Add Some Overhead (excess capacity for future needs and capacitor aging). That decision is up to you.

But most important not to miss: "The recommended total Power Supply Wattage gives you a general idea on what to look for BUT it is NOT a crucial factor in power supply selection! Total Amperage Available on the +12V Rail(s) is the most important, followed by the +5V amperage and then the +3.3V amperage."

Your card, if it uses 150watts at 12v will pull 12.5 amps from the 12v rail. So a power supply with only 18 amps on the 12v rail would be iffy.
A crude rule of thumb is to take the total wattage needed and divide by 12. This is the minimum number of amps on the 12v rail you would want. That result will skew higher than necessary, but that will never hurt you.

 

[Kenter]

Thanks, found that IF i would buy this graphics card, then i would have ~100W free. Required power was 309W.

 

[essenbe]

That would depend on the brand of power supply you have. I always recommend Corsair, Seasonic or Antec. Those are quality PSUs and will put out what they claim to put out. Some of the cheaper PSUs although rated as 400W, will not put that much out. Plus, I would want more headroom than 90W. You will be limited on future upgrades and it will run hotter.

 

[kbrady1979]

Essenbe is right. Corsair, SeaSonic, and Antec are very popular and actually put out the power that is advertised. For your situation, I would look at something like this: Corsair CX500M

If you are thinking of upgrading your entire PC anytime soon, I might look into something more appropriate.

 

[stormy13]

Thanks, found that IF i would buy this graphics card, then i would have ~100W free. Required power was 309W.

Sorry to say, but no you don't. That 400W total for the power supply includes both the 3.3V and 5v rails as well as the 12V rail(s). It should be OK if is is a good quality 400W. If it is a no name cheapy, then I wouldn't risk it.

 

[AddRAM]

This is a good price for a 750 watt PSU

CORSAIR HX Series HX750 750W ATX12V 2.3 / EPS12V 2.91 SLI Ready CrossFire Ready 80 PLUS GOLD Certified Modular Active PFC Power Supply - Newegg.com

 

[mjf]

I'm not sure when graphics card manufacturers mean when they specify a minimum PSU rating. I have taken it as a rule of thumb rating for your total system but then that of course depends on other elements. For example I have a Nvidia GTS450 and they say minimum PSU 400W or greater - I don't think the graphics card is going to suck 400W. I do think the 12v current rating is a key parameter.
The calculator program referenced earlier is more accurate. But to give you my general opinion I'd go for at least 500W+. A quality PSU is a key element and some extra watts isn't going to cost you that much.

 

[TVeblen]

I agree that the power supply recommendations are a crude tool. They basically assume that everyone's PC is the same setup - (probably an HP).

The thing that annoys me most with video card specs is that the one piece of information you really need - the Amps drawn - is either non existent or buried deep in the product documents. That should be front & center in any sales ad for a video card IMHO.