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23 Mar 2013   #1

Windows 7 64bit
 
 
Help

I have two pny 670 video card an I asking what power supply should I use my pc have 875 power supply is that enough power to run? An video cards are 550 watts got 2 of them thx

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23 Mar 2013   #2

 

A quality-made 550W PSU is more than enough (I can prove it).

However, which 875W PSU do you have? What's the make and model? I don't know of any 875W PSUs that are safe to use.
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23 Mar 2013   #3

Windows 7 Home Premium 64 Bit SP1
 
 

875w PSU sounds like it is OEM from Alienware/Dell.

When a graphics card says it requires 550 watts it is describing the power draw on your entire system not just the graphics card by itself. With another pny670 you might be looking at an additional 150w draw in addition to the recommended 550watts. You say you have a 875w PSU so you should be fine running SLI.
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23 Mar 2013   #4

Windows 7 Pro X64 SP1
 
 

EVGA | Products | EVGA GeForce GTX 670 | 02G-P4-2670-KR

For a single card, eVGA recommends a 500W PSU with a minimum of 30A available at +12V. eVGA also claims that the card consumes 170W.

So, if your PSU can provide at least 45A at +12V, you should be OK. (That would max out a good 550W PSU. You probably want more margin.)
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23 Mar 2013   #5

 

Quote   Quote: Originally Posted by Quadra View Post
875w PSU sounds like it is OEM from Alienware/Dell.

When a graphics card says it requires 550 watts it is describing the power draw on your entire system not just the graphics card by itself. With another pny670 you might be looking at an additional 150w draw in addition to the recommended 550watts. You say you have a 875w PSU so you should be fine running SLI.
The PSU requirements stated by both AMD and NVIDIA are referring to peak-rated PSUs. The typical 550W peak-rated PSU has a +12V capacity of about 396W (33A), sometimes less. A good PSU is rated based on its continuous capacity. There are a few good 400W (continuous-rated) PSUs that have a +12V capacity of 396W.

Check this out:

GeForce GTX 670 2 and 3-way SLI review - Power Consumption

With one GTX 670 under full load in their system, their PSU pulled 279W from the wall outlet. Their CPU was idling, so I have to add 130W for the i7-970 under full load. So if the GTX 670 and the i7-970 are under full load simultaneously, then the PSU would be pulling 409W from the wall outlet. Therefore, if the PSU is 85% efficient while pulling 409W from the wall outlet, then the system is pulling 347W from the PSU. Although, this is an unrealistically high power draw. A more realistic power draw is seen while gaming, and that would be closer to about 300 to maybe 350W tops. This means any quality-made 400W PSU is more than enough because such a quality-made PSU can deliver 400W 24/7 if it's ever needed.

With two GTX 670s under full load in their system, their PSU pulled 433W from the wall outlet. Adding 130W for the CPU again, it comes out to 563W being pulled from the wall outlet. So if the PSU is 85% efficient while pulling 563W from the wall outlet, then that means the system is pulling 478W from the PSU. Of course, the gaming power draw would be about 425 to maybe 475W. This means a quality-made 550W PSU is more than enough because such a PSU can deliver 550W 24/7 if it's ever needed.


Quote   Quote: Originally Posted by bobkn View Post
EVGA | Products | EVGA GeForce GTX 670 | 02G-P4-2670-KR

For a single card, eVGA recommends a 500W PSU with a minimum of 30A available at +12V. eVGA also claims that the card consumes 170W.

So, if your PSU can provide at least 45A at +12V, you should be OK. (That would max out a good 550W PSU. You probably want more margin.)
30A is is 360W, and that's the typical +12V capacity of a peak-rated 500W PSU. There are many 400W PSUs that have a +12V capacity of 360W. Some of them are rated at 430W because of the +5V and +3.3V rails.

Check out the break-down of the power consumption I posted above.
My System SpecsSystem Spec
23 Mar 2013   #6

Windows 7 Pro. 64/SP-1
 
 

Why would anybody want a power supply so lacking in watts that it has to work at 70, 80 or even 90% of it capabilities. It does not make sense to me.

I personally don't care what the electrical formulas and charts indicate. The formulas work good in passing test in computer science 102.
Put a quality power supply in the computer that only has to work 30,40 or 50% of it capabilities when a load is put on it. It will run cooler, quieter and longer.

Here is my method.
What ever the max demand of the computer could be, add 200W or more with a quality brand such as Corsair or Seasonic. They will have the proper amps per rail because they are quality. The price difference is minimal. Never cheat your computer with a just get by power supply.
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23 Mar 2013   #7

 

Quote   Quote: Originally Posted by Layback Bear View Post
Why would anybody want a power supply so lacking in watts that it has to work at 70, 80 or even 90% of it capabilities. It does not make sense to me.

I personally don't care what the electrical formulas and charts indicate. The formulas work good in passing test in computer science 102.
Put a quality power supply in the computer that only has to work 30,40 or 50% of it capabilities when a load is put on it. It will run cooler, quieter and longer.

Here is my method.
What ever the max demand of the computer could be, add 200W or more with a quality brand such as Corsair or Seasonic. They will have the proper amps per rail because they are quality. The price difference is minimal. Never cheat your computer with a just get by power supply.
The kind of PSUs I'm talking about would have absolutely no problem. I'm not talking about ultra high-end PSUs that cost "an arm and a leg" either. Powering a system that has two GTX 670s and an i7-970 at stock with a quality-made 750W is absolutely ridiculous, it's totally unnecessary, and it's a huge waste of money. Ask any real PSU expert. Don't just take my word for it.

If you think I don't know what I'm talking about, then ask about me over at Overclock.net. To be quite honest, I'm getting a little tired of how you've contradicted me just about every time I have posted about PSUs since the day I joined. It kind of makes me want to stop coming here.
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23 Mar 2013   #8

Win7 Pro SP1 64
 
 

Quote   Quote: Originally Posted by TwoCables View Post
Quote   Quote: Originally Posted by Layback Bear View Post
Why would anybody want a power supply so lacking in watts that it has to work at 70, 80 or even 90% of it capabilities. It does not make sense to me.

I personally don't care what the electrical formulas and charts indicate. The formulas work good in passing test in computer science 102.
Put a quality power supply in the computer that only has to work 30,40 or 50% of it capabilities when a load is put on it. It will run cooler, quieter and longer.

Here is my method.
What ever the max demand of the computer could be, add 200W or more with a quality brand such as Corsair or Seasonic. They will have the proper amps per rail because they are quality. The price difference is minimal. Never cheat your computer with a just get by power supply.
The kind of PSUs I'm talking about would have absolutely no problem. I'm not talking about ultra high-end PSUs that cost "an arm and a leg" either. Powering a system that has two GTX 670s and an i7-970 at stock with a quality-made 750W is absolutely ridiculous, it's totally unnecessary, and it's a huge waste of money. Ask any real PSU expert. Don't just take my word for it.

If you think I don't know what I'm talking about, then ask about me over at Overclock.net. To be quite honest, I'm getting a little tired of how you've contradicted me just about every time I have posted about PSUs since the day I joined. It kind of makes me want to stop coming here.
I do not think it is ridiculous . I have a 700 Watt PSU and I am getting by with it and I only have one GTX 460. If you get a PSU that will be overloaded you will be taking a chance of blowing it and other components. Just because My PSU is a 700 watt PSU does not mean that it uses all of it's power. It is far better to have more than you need than less. This is a Tech Forum and yes some members will disagree with you. I personally do not overclock and couldn't care less about some other forum you post at.
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23 Mar 2013   #9

 

Quote   Quote: Originally Posted by Gary View Post
I do not think it is ridiculous . I have a 700 Watt PSU and I am getting by with it and I only have one GTX 460. If you get a PSU that will be overloaded you will be taking a chance of blowing it and other components.
Only with a low-quality or a generic PSU. The kind of PSUs I am talking about would harmlessly turn off. However, that would never happen because the power consumption is well below the PSU's continuous rating. Let's say that I'm talking about a quality-made 400W PSU that can deliver 400W 24/7 at internal PSU temperatures up to 50C. That means that a 350W power draw is absolutely nothing for that PSU. That's basically a walk in the park for it.


Quote   Quote: Originally Posted by Gary View Post
Just because My PSU is a 700 watt PSU does not mean that it uses all of it's power.
Yeah, I know that, but this has nothing to do with what I'm talking about.

Anyway, which 700W PSU do you have? What is the make and model?


Quote   Quote: Originally Posted by Gary View Post
It is far better to have more than you need than less. This is a Tech Forum and yes some members will disagree with you. I personally do not overclock and couldn't care less about some other forum you post it.
I'm not talking about overclocking. I'm talking about asking them over there about me so you can find out what they say about me in regards to what they think I know about PSUs. Maybe you guys will change your opinion about me because right now it seems like I'm being judged as the new guy who doesn't know anything.
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23 Mar 2013   #10

Win7 Pro SP1 64
 
 

It is two years old made by Coolermaster. I doubt that model is still being built.
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