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Question about Video card and Power Supply CompatabilityFollow

#1 Jan 05 2011 at 7:15 PM Rating: Good
I'm buying this computer here pretty soon, but I'd like to upgrade the graphics card. I'm a bit confused about making sure that the power supply will be able to handle it though.

I'm looking to upgrade with this graphics card. It says that it needs a 450 watt power supply, and the computer has a 500 watt power supply. Does this allowance of 450 include the processor? I looked it up, and the processor uses 65 watts, so I'm trying to figure out if I need to upgrade the power supply as well.

I'm also wondering if the computer has a wireless internet card. I'm assuming that since the details do not say that it does, that it more than likely does not and that's something else I'll need to purchase.
#2 Jan 05 2011 at 8:05 PM Rating: Excellent
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Newegg actually has a power supply calculator. Or you can enter "power supply calculator" into Google and find some various other ones if you want more than one opinion (Newegg's doesn't ask half as many questions as some of them). Some folks don't care for them but I've found them more helpful.

My main caveat is that the page you linked doesn't mention (that I saw) the make/model of the PSU and they are not all created equally. If you're close to the recommended allowance, I'd play it safe and assume you're getitng some low end PSU and upgrade now to a beefier brand you can trust than skate the edge with one of questionable quality.

Edited, Jan 5th 2011 8:07pm by Jophiel
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Belkira wrote:
Wow. Regular ol' Joph fan club in here.
#3 Jan 05 2011 at 8:31 PM Rating: Good
You mean the PSU for the computer doesn't have a brand listed? I've looked at other PC's on newegg and it seems to be pretty common for the brand name of different peripherals to not be listed. I'm assuming it would be listed on the box or in the manual or something.

That is a neat tool, but it's only served to confuse me further lol. I checked both the newegg calc, and one from antec, and they both are saying that I'd only need 300-350 watts. That can't possibly be correct, when the stats listed on the graphics card says it needs a minimum of 450. Unless that's just a recommendation for the wattage of the PSU that you use with the video card, and not how much it actually uses?
#4 Jan 06 2011 at 12:31 AM Rating: Decent
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It's just a recommendation, correct. A PSU that claims 450 watts of output will not actually deliver that much at full load, so while your setup only needs 300-350 watts, you might only be getting that much instead of the full 450 the box claims.
#5 Jan 06 2011 at 12:45 AM Rating: Excellent
Liberal Conspiracy
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PigtailsOfDoom wrote:
You mean the PSU for the computer doesn't have a brand listed?

Correct. It's important in that some PSU manufacturers are more liberal in their interpretation of what "500 W" means than others which in turn leads to video card makers overestimating the amount of "power" you need on the assumption that your PSU is a piece of junk.
lolwiki wrote:
The power rating of a PC power supply is not officially certified and is self-claimed by each manufacturer. A common way to reach the power figure for PC PSUs is by adding the power available on each rail, which will not give a true power figure. Therefore it is possible to overload a PSU on one rail without having to use the maximum rated power.
[...]
This tendency has led in turn to greatly overspecified power supply recommendations, and a shortage of high-quality power supplies with reasonable capacities. Very few computers require more than 300–350 watts maximum.
____________________________
Belkira wrote:
Wow. Regular ol' Joph fan club in here.
#6 Jan 06 2011 at 3:51 AM Rating: Good
Okay, thanks guys. For now I'll just stick with the power supply that's already in the pc. If the upgrade video card doesn't work with it, I can always buy a bigger one at that point. Sounds like that won't be an issue though.
#7 Jan 06 2011 at 3:19 PM Rating: Good
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It's not uncomoon for generic PSU's to only be reliable to 60-65% of their rated output under full load. Over time, they may degrade and only be reliable as low as a 40% load. Some companies "cheat" and list their output based on 20-50% load. If it is an 80+ Certified PSU (will have a logo for it on the box somewhere), it means the PSU is tested to give the rated wattage at 80% load. Most systems with a high nd card can get by with a steady 400 watts of continuous power (the Uber cards/systems will need more). So, you kinda have two rules to go by:

If it's 80+, divide the required wattage by 0.80 and shoot for a rating of that or higher. (400/0.80=500)

If it's not 80+, divide the required wattage by 0.60 and shoot for that rating or higher. (400/0.60=667)

I know this may seem a bit extreme, but this is to guard against unknowns--number of drives, fans and other cooling devices, overclocking, and future expansion, etc.

Corsair has an app where you can specify your CPU, graphics card, number of drives, and whether you overcock CPU/GPU. It's a bit biased of course and only gives you results for their 80+ models, but it will give you several recommendations ranging from minimum, middle of the road, and lots of headroom. Bear in mind these ARE 80+ PSU's, so if it gives you a 450W result, that is an 80+ model (360W reliable at 80% load):

http://www.corsair.com/learn_n_explore?psu=yes

Raist
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