What is the PSU sweetspot?

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#1 Posted by homeboylizard (1289 posts) -

Well, I know a lot of you are saying that a 750W power supply is the best, but seeing how newer cards have lower cosumption, due to better architecture, is 750W an overkill?

I myself have a 650W Seasonic running a GTX 570, i5 2310, 2 HDDs, 1 SSD, 2 case fans and always 2 more external hard drives and the PSU fan never got off.

Also, I have been looking to upgrade some of my parts, and I read that a lot of people are running sli GTX 680's on 620W PSU's, but I don't know if it is really smart.

So, is 750 W still the best, or the sweetspot got lower over time?

#2 Posted by V4LENT1NE (12895 posts) -
Any recent single GPU can likely run on a 500W PSU with ease.
#3 Posted by GTR12 (9244 posts) -

I say 650, just an opinion but running 2 power hungry cards is enough justification.

#4 Posted by kraken2109 (13010 posts) -

I'd recommend 550-600w for single cards and 750w for dual cards.

#5 Posted by Blistrax (1071 posts) -
Use a calculator like the one at Thermaltake: http://www.thermaltake.outervision.com/ Use a couple of different ones and then beef up, like divide by 0.8. The bigger PSUs are built to dissipate more heat, so if you're running a PSU near its max, you're stressing it. My rig comes to 701, and I'm running an 850. Better safe than sorry. The slightly lesser efficiency of a PSU running in overkill is negligible.
#6 Posted by LordEC911 (9972 posts) -

Use a calculator like the one at Thermaltake: http://www.thermaltake.outervision.com/ Use a couple of different ones and then beef up, like divide by 0.8. The bigger PSUs are built to dissipate more heat, so if you're running a PSU near its max, you're stressing it. My rig comes to 701, and I'm running an 850. Better safe than sorry. The slightly lesser efficiency of a PSU running in overkill is negligible.Blistrax


Ummm.... what?
And FYI your rig uses ~500w.

@OP, sweet spot really depends on what you are doing.
A quality 400w is going to easily run all single GPU setups.
Quality 500-600w are going to run the majority of dual card setups.

As far as pricing though, quality 500-600w PSUs can be found in the $60-$70 range and high quality 650-750w PSUs around $100.

#7 Posted by 04dcarraher (19328 posts) -
Always grab more then what you need, psu's lose their ability to produce their maximum wattage as they age. Gaming systems and plan on transferring psu through one upgrade to another get at least a 650w.
#8 Posted by XaosII (16565 posts) -

You should calculate it. My file server uses up about 47W. Yes 4 and 7 put together. Why would i want a 450W, or even a 200W PSU?

#9 Posted by 04dcarraher (19328 posts) -

[QUOTE="Blistrax"]Use a calculator like the one at Thermaltake: http://www.thermaltake.outervision.com/ Use a couple of different ones and then beef up, like divide by 0.8. The bigger PSUs are built to dissipate more heat, so if you're running a PSU near its max, you're stressing it. My rig comes to 701, and I'm running an 850. Better safe than sorry. The slightly lesser efficiency of a PSU running in overkill is negligible.LordEC911



Ummm.... what?
And FYI your rig uses ~500w.

@OP, sweet spot really depends on what you are doing.
A quality 400w is going to easily run all single GPU setups.
Quality 500-600w are going to run the majority of dual card setups.

As far as pricing though, quality 500-600w PSUs can be found in the $60-$70 range and high quality 650-750w PSUs around $100.

That is false, A 400w will not run all single gpu setups. If you have a top tier gpu that uses 200+w and you have a cpu that is normally 125w TDP and you overclock your going to be stressing that psu to the brink. 400w psu's are not designed to handle large 12v rail loads, and do not have the pci-e connectors to support a gpu with a 6 or 8 pin and another 6 pin. And using 4 pin molex adapters isnt smart because that's too much current on the line .

#10 Posted by Klunt_Bumskrint (3715 posts) -
I had an Antec 650w before my TX850 and it worked fine with my SLI but I'd constantly be thinking it was going to break. I upgraded to ease my mind.
#11 Posted by 04dcarraher (19328 posts) -

I had an Antec 650w before my TX850 and it worked fine with my SLI but I'd constantly be thinking it was going to break. I upgraded to ease my mind.acanofcoke
Your 650w was being stressed, but not to its limit, 680's at 1200mhz is like 220-230w a piece along with a i7 at 4.5 ghz which would be around 100w rdp. so you were looking at 560-580w at best for the whole system being 540w+ on the 12v rail at full load.

#12 Posted by Blistrax (1071 posts) -

[QUOTE="Blistrax"]Use a calculator like the one at Thermaltake: http://www.thermaltake.outervision.com/ Use a couple of different ones and then beef up, like divide by 0.8. The bigger PSUs are built to dissipate more heat, so if you're running a PSU near its max, you're stressing it. My rig comes to 701, and I'm running an 850. Better safe than sorry. The slightly lesser efficiency of a PSU running in overkill is negligible.LordEC911



Ummm.... what?
And FYI your rig uses ~500w.

@OP, sweet spot really depends on what you are doing.
A quality 400w is going to easily run all single GPU setups.
Quality 500-600w are going to run the majority of dual card setups.

As far as pricing though, quality 500-600w PSUs can be found in the $60-$70 range and high quality 650-750w PSUs around $100.

It must be nice to have a magic ass you can just pull information from when you need it.
#13 Posted by LordEC911 (9972 posts) -

That is false, A 400w will not run all single gpu setups. If you have a top tier gpu that uses 200+w and you have a cpu that is normally 125w TDP and you overclock your going to be stressing that psu to the brink. 400w psu's are not designed to handle large 12v rail loads, and do not have the pci-e connectors to support a gpu with a 6 or 8 pin and another 6 pin. And using 4 pin molex adapters isnt smart because that's too much current on the line.04dcarraher

Nope, what I said was true. YOU made it false by pulling a strawman and adding in the overclocking...

A quality 400w PSU is going to be able to handle as large of a 12v load as any other quality PSU, which is generally 90-100% of the rated wattage.
You should also look up some details on the QUALITY 300-400w PSUs, they come with either a 6pin or 8pin pci-e connector.
Using 4pin molex adapters is just fine... why would people/companies make/use them if they didn't work?

@Blistrax- Wow... keep it classy there. I'm sorry you don't like good accurate info.

#15 Posted by 04dcarraher (19328 posts) -

When you have 400w psu trying to fill a role of a 500w+ psu your going to run into issues now or later. Even though you theoretically could run a system does not mean you can or you should . 400-450ww psu, at best come with one pci-e power connector, which means its only designed for set amount of usage. You should know better then to claim that any single gpu system can be ran on a good quality 400w psu. Also using the 4 pin molex pci-e adapter is an excuse because those adapters are only suppose be a supplement not take the place of a real 75w pci-e connector. In reality your shouldnt go beyond 35watts with a 4 pin molex for safe and long tern use.

#16 Posted by FaustArp (1038 posts) -
I had an Antec 650w before my TX850 and it worked fine with my SLI but I'd constantly be thinking it was going to break. I upgraded to ease my mind.acanofcoke
Pretty much the same story here lol. I bought my Corsair TX850M when I bought my 2nd GPU. I wasn't even going to try the one I had.
#17 Posted by LordEC911 (9972 posts) -

When you have 400w psu trying to fill a role of a 500w+ psu your going to run into issues now or later. Even though you theoretically could run a system does not mean you can or you should . 400-450ww psu, at best come with one pci-e power connector, which means its only designed for set amount of usage. You should know better then to claim that any single gpu system can be ran on a good quality 400w psu. Also using the 4 pin molex pci-e adapter is an excuse because those adapters are only suppose be a supplement not take the place of a real 75w pci-e connector. In reality your shouldnt go beyond 35watts with a 4 pin molex for safe and long tern use.04dcarraher

*Facepalm*

You aren't using a 400w to fill a 500w role, you are saying to use a 500w to power ~300-350w which can be done on a quality 400w PSU.
There are 450w PSUs that come with dual 8pin pci-e connectors FYI.

#18 Posted by 04dcarraher (19328 posts) -

[QUOTE="04dcarraher"]When you have 400w psu trying to fill a role of a 500w+ psu your going to run into issues now or later. Even though you theoretically could run a system does not mean you can or you should . 400-450ww psu, at best come with one pci-e power connector, which means its only designed for set amount of usage. You should know better then to claim that any single gpu system can be ran on a good quality 400w psu. Also using the 4 pin molex pci-e adapter is an excuse because those adapters are only suppose be a supplement not take the place of a real 75w pci-e connector. In reality your shouldnt go beyond 35watts with a 4 pin molex for safe and long tern use.LordEC911

*Facepalm*

You aren't using a 400w to fill a 500w role, you are saying to use a 500w to power ~300-350w which can be done on a quality 400w PSU.
There are 450w PSUs that come with dual 8pin pci-e connectors FYI.

Now your saying 450w, make up your mind is it 400w or 450w? A high quality 450w is about equal to a decent 500-550w. which why I stated 400w is trying to fill the role of a 500w. For what you pay for a high quality 450w that does have 2 pci-e connectors you can pick up a good to high quality 550-650w+ psu for nearly the same price. Also lets not forget psu's over time lose their ability to provide their max wattage output. so getting a psu that just does the system is not a smart idea if you plan on using the psu in the long term with upgrades or new system later on.

#19 Posted by homeboylizard (1289 posts) -
From the info on here it's like this: 1 GPU=500W to be safe, but 450W is enough. 2 GPU= 750W to be safe, but 650W is enough. But, the best thing to do is when buying a 2nd GPU is to buy a good, 850W PSU (incase for a 3rd GPU)?
#20 Posted by 04dcarraher (19328 posts) -

From the info on here it's like this: 1 GPU=500W to be safe, but 450W is enough. 2 GPU= 750W to be safe, but 650W is enough. But, the best thing to do is when buying a 2nd GPU is to buy a good, 850W PSU (incase for a 3rd GPU)?homeboylizard
It all depends on the hardware usage needs, and future proofing yourself, also quality of the psu matters too. Say you have a system that draws 410w at most, you dont go out and buy a 450w psu and expect it to keep up after a set amount of time. You always grab a psu at least 100w more then you need to allow breathing room for upgrades and to allow long term use of the PSU. Since psu's over time lose their ability to provide their max wattage output as the capacitors age.

#21 Posted by _SKatEDiRt_ (2570 posts) -
I have an ocz 700watt. Never a single problem. Not really such thing as a sweet spot just as long as everything has enough power