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PSU question?

PostPosted: Thu Mar 03, 2011 9:17 am
by Shyrtandros
I have the basic (and not so good) 300W PSU in my rig.

It's a quad core and I just got a PNY GT 240 (for half price!) I know it recommends at a minimum to use a 350w with a 12v+ 18A.

Since I do use this to play WoW / Rift or w/e does anyone have any recommendations?

I was thinking of grabbing a 500w but I also saw a deal for a 750w.
I'm not sure if the 750w would be overkill?


Thanks.

Re: PSU question?

PostPosted: Thu Mar 03, 2011 9:28 am
by cerwillis
Shyrtandros wrote:I have the basic (and not so good) 300W PSU in my rig.

It's a quad core and I just got a PNY GT 240 (for half price!) I know it recommends at a minimum to use a 350w with a 12v+ 18A.

Since I do use this to play WoW / Rift or w/e does anyone have any recommendations?

I was thinking of grabbing a 500w but I also saw a deal for a 750w.
I'm not sure if the 750w would be overkill?


Thanks.

I'd say that you would probably be just fine with a 500w, but a 750w is what I run, and would give you room to upgrade video cards, etc if you feel the need. I've had This One for about a year and it rocks.

Re: PSU question?

PostPosted: Thu Mar 03, 2011 2:01 pm
by razul
I've always had good luck with ultra
http://www.tigerdirect.com/applications ... ULT-LSP650
as for wattage, I generally like getting at least a bit of overkill. My rig has a 600w psu, even though I'm only using 450w or so. (It's an old rig I'll be replacing soon)

Re: PSU question?

PostPosted: Thu Mar 03, 2011 3:05 pm
by Gladia
If your curious, This will give you an idea of what size power supply you need.

I would say 500 is probably more than enough, i run a core i7 @ 4ghz, water cooled(pump/3-120mm fans), 6 2tb hdd's, 12gb ram, and a 5870 off a 750w, and still have more headroom power wise.

Re: PSU question?

PostPosted: Thu Mar 03, 2011 7:26 pm
by Talaii
Bear in mind, too: There are (at least over here) a LOT of cheap and nasty $20-40 power supplies that claim to have high wattage. They generally have weak 12V rails (not enough amps, most of your power draw will be off the 12V rail, as it's used for the CPU and Graphics card), or just straight fake their figures. Go for a decent brand (you can generally find online reviews of the power supply models, use that to check that it'll run fine).

I have a 500W antec PSU, and it runs my i5/5850/lots of disks system without a hitch. 500 should be more than you need - graphics card manufacturers tend to overestimate the power requirements by a lot, partially to make up for the aforementioned cheap power supplies, and partially because older power supplies tend to have weaker 12V rails (older computers used a lot more on the 5V rail, and a lot less on the 12V). Note that 18A on the 12V rail is 216W of power, not 350; and the card itself has a TDP* of 69W, so unless you overclock it'll use less than that. It's hard to estimate actual power draw for the whole system though: Easier for you to plug everything into that power supply calculator above.




*: TDP = thermal design power. This number indicates to the card manufacturers the maximum amount of heat that the chip will generate, so they can design a cooling solution appropriate to it. Basically: At standard clock speeds, the power draw will never exceed this.

Re: PSU question?

PostPosted: Thu Mar 03, 2011 7:45 pm
by Fivelives
There is no such thing as "too much" power supply. Check out Tom's Hardware for reviews on them though - it's a very thorough and comprehensive review site for hardware stuff:

http://www.tomshardware.com/s/reviews/power-supply/

Re: PSU question?

PostPosted: Fri Mar 04, 2011 10:00 am
by Shyrtandros
From what I've read and seen others say they have it looks like Antec or Corsair are the best options for reasonable pricing?

Re: PSU question?

PostPosted: Mon Mar 07, 2011 12:25 pm
by fafhrd
I got a Corsair 650 a few years back that I've been running without issues, even with a new GTX580 in it.

Keep in mind that the system will only draw as much power as it needs, so even if you have a 1000W PS, if your system only need 250 it'll just draw 250 - your power bill won't go up just because you bought a better powersupply. Also be careful about deals that are too good to be true, unless it's from a known and trusted brand it probably is too good to be true. Cheap brands will either flat out lie, or label their supply with the maximum possible wattage it could ever support, while companies like Corsair will usually label with slightly lower wattage than they are comfortable with.

Also, powersupplies degrade over time. I've never managed to get a straight answer on how exactly, but apparently they will lose 5-10% of their peak wattage over a few years of use, so having more room to grow is good.

Finally, the power requirement listed for the card is usually its max draw under load - it won't always be drawing the full wattage it asks for.

Re: PSU question?

PostPosted: Wed Mar 09, 2011 2:58 pm
by laterna
Keep in mind that a PSU is more efficient when its run at 40-60% of its listed Wattage. Personally I run a 500W machine on a 850W PSU. You're looking at a very steep efficiency fall curve when you're running your PSU at 90% of your listed wattage. So in the long run, you lose money instead of the cash you saved from getting a cheaper one :)

Re: PSU question?

PostPosted: Sun Mar 13, 2011 9:09 pm
by Halcya
fafhrd wrote:Also, powersupplies degrade over time. I've never managed to get a straight answer on how exactly, but apparently they will lose 5-10% of their peak wattage over a few years of use, so having more room to grow is good.


The capacitors in the PSU utilize a chemical process to store and release electricity. As with all chemical processes, it is not a 100% efficient reaction, and thus there is a small decomposition of product as the reactions occur. This results in the the chemical viability of the capacitor decreasing over time along with a decline in the peak wattage. Given a long enough time frame the capacitor will eventually fail as the chemicals are used up completely. For most PSUs, though, the rate of decomposition is slow, but you can still see a 5% to 30% degradation in performance over five years (depending both on quality of the capacitor and load on the PSU--lower quality capacitors will degrade by large percentages in a short period). Maintaining a lower percentage of load helps extend the capacitor life (and thus PSU life) by reducing the number of reactions occurring in each capacitor.