Just a quick Q

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Just a quick Q

Postposted on Sat Jul 20, 2013 10:16 am

I'm putting together an uber cheap PC for my younger bro, as he likes his OLD PC games (he uses his xbox for anything modern). Saving money, i'm giving him my old GeForce 8800 GTS. What power supply should i get? Since the card is 6 years old, you'd presume it wouldn't need to be that beefy. but then again, the older cards were more power hungry, weren't they?
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Re: Just a quick Q

Postposted on Sat Jul 20, 2013 10:44 am

You won't need anything massive. Look for a name brand good quality power supply in the 500-600 watt range. As long as you don't start SLI'ing the cards or running a massive amount of hdd's off it, you'll be fine.


I'm actually running a 7870 off a Corsair 430 watt power supply.
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Re: Just a quick Q

Postposted on Sat Jul 20, 2013 10:47 am

hmm, was hoping to go lower than that... oh well
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Re: Just a quick Q

Postposted on Sat Jul 20, 2013 11:20 am

http://www.thermaltake.outervision.com

Use this to calculate your wattage requirement. Keep in mind that PSU's are generally most efficient at 20-25% usage.
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Re: Just a quick Q

Postposted on Sat Jul 20, 2013 11:21 am

The GeForce 8800GTS has only one 6-pin PCIe connector. You don't need a large power supply. TR's test system with the GeForce 8800GTS 640MB pulled 254 watts from the wall. Figuring in the 82% efficiency of the power supply that they used, that's only an average continuous consumption of 208 watts inside the case. Add 40% to that to handle peaks and to provide a safety margin, and you'd still be able to get away with a good quality power supply that could provide 25 amperes (300 watts) on the +12 volt rail.

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$45 Antec EA-380D (Bronze, 28A @12V)
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$64 SeaSonic SSR-360GP (Gold, 30A @12V)
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Re: Just a quick Q

Postposted on Sun Jul 21, 2013 7:23 pm

Antec Earthwatts 380W, frequently on sale, plenty capable of supporting 150W cards, as I did with one for several years on an already old Antec 380W.

You're looking at 200W peak draw from a non-overclocked system with an 8800GTS. 400W PSU is the most you're gonna need, and that's being both cautious and aiming for peak efficiency.
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Re: Just a quick Q

Postposted on Sun Jul 21, 2013 7:52 pm

Here's another choice: http://www.newegg.com/Product/Product.a ... 6817151077 350W might sound low, but Seasonic makes good PSUs. If we had an idea of the rest of the system that might help us know how much headroom to allow, 350W (it can deliver 324W on the 12V rail) ought to be sufficient unless it's a highly overclocked or notoriously inefficient CPU/motherboard. If it's a 45nm Core 2 (which can be had for peanuts nowadays) or later mainstream Intel CPU it would be fine.
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Re: Just a quick Q

Postposted on Mon Jul 22, 2013 12:37 am

Star Brood wrote:http://www.thermaltake.outervision.com

Use this to calculate your wattage requirement. Keep in mind that PSU's are generally most efficient at 20-25% usage.

Should be in the 30-80% load range I believe, of course, the higher the rating the larger the range.
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Re: Just a quick Q

Postposted on Mon Jul 22, 2013 7:10 am

Flying Fox wrote:Should be in the 30-80% load range I believe, of course, the higher the rating the larger the range.


I guess it depends on which review site you're following. Every PSU review I've read has the best efficiency curve at 20-25% and slowly starts to drop off up until their rated efficiency and then quickly drops off.

Then again, I haven't read a TechReport PSU review. Have you guys ever done one?
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Re: Just a quick Q

Postposted on Mon Jul 22, 2013 10:19 am

Star Brood wrote:
Flying Fox wrote:Should be in the 30-80% load range I believe, of course, the higher the rating the larger the range.


I guess it depends on which review site you're following. Every PSU review I've read has the best efficiency curve at 20-25% and slowly starts to drop off up until their rated efficiency and then quickly drops off.

Then again, I haven't read a TechReport PSU review. Have you guys ever done one?

The latest from SPCR and Jonny Guru seem to be near 50%. TR's own review from 3 years ago is the contrarian.

Besides, on a modern system that uses around 200W, getting a 800W unit is almost an exercise in overkill. And in places where electricity prices are not too high, you are not going to make the difference in the purchase price during the lifetime of the system. In the end it is more like feeding the PSU companies.
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Re: Just a quick Q

Postposted on Mon Jul 22, 2013 12:13 pm

Star Brood wrote:Every PSU review I've read has the best efficiency curve at 20-25% and slowly starts to drop off up until their rated efficiency and then quickly drops off.


As a rule of thumb, I generalise that all PSU's work close to their best at 50% load:
Most PSU's peak between 25% and 50% load. However, they're almost all lousy below 25%, whilst most of them retain high efficiency way past 50%
Given how people seem intent on using a 650W PSU to power a machine that idles at 90W and peaks at 200W, I'd always aim to go slightly over 50% rather than under, because some name-brand PSU's are truly awful below 25%
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Re: Just a quick Q

Postposted on Mon Jul 22, 2013 10:26 pm

One thing to remember in the name of choosing the best PSU wattage based on efficiency percentage is the absolute amounts as well. A 10% or 20% total efficiency difference at low modern idle load wattages isn't very much in absolute terms. This is sort of a corollary to what Flying fox said.

I would say that Bronze is still fine if you can get a good deal and want to save money while still getting a good PSU, Gold PSUs have been reasonably affordable for a while, but the last I looked Platinum PSUs were way overpriced for the difference versus Gold.
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