# Thread: How to calculate maximum power consumption on a graphics card

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## How to calculate maximum power consumption on a graphics card

I thought well if the GPU has one 6 pin and one 8 pin connector (that's the case of the GTX 580)

so that should be 75W for the 6 pin + 150W for the 8 pin + 75W from the PCIe slot.

That gives us a total of 300W

but I find this:

https://www.techpowerup.com/reviews/...TX_580/25.html

So how come the GTX 580 drew 304W even If it is not overclocked?

What is the maximum 3.3 V rail power consumption you have seen on a VGA? Is it really that high?

Any ideas on how to accurately estimate power draw of a GPU without underestimating or overestimating?

2. The 300w limit set by the PCI-SIG is a "soft" limit. The products that are PCIe compliant should not exceed that limit based on the interfaces. In practice, they can do this rather often.
You realize how absurd these limits are as well, when the 8pin PCIe cable has three 12v cables coming from the PSU and five ground wires while the 6pin cable is three 12v & three ground. So why with the same number of power sources is the 8pin cable able to deliver twice the capacity?

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GDILord (05-20-2018)

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Originally Posted by Tator Tot
The 300w limit set by the PCI-SIG is a "soft" limit. The products that are PCIe compliant should not exceed that limit based on the interfaces. In practice, they can do this rather often.
You realize how absurd these limits are as well, when the 8pin PCIe cable has three 12v cables coming from the PSU and five ground wires while the 6pin cable is three 12v & three ground. So why with the same number of power sources is the 8pin cable able to deliver twice the capacity?
Thanks, I never get the 8 pin vs 6 pin thing, how can the 8 pin provide more power if it has the same number of 12V cables

5. Originally Posted by COFASA
Thanks, I never get the 8 pin vs 6 pin thing, how can the 8 pin provide more power if it has the same number of 12V cables
As I said, the limit is "artificial" or "soft" and doesn't actually exist. The pins and wires can handle the extra current on the 6pin connector but way back PCI-SIG wanted to make an 8pin connector for higher draw components. Originally you were going to have a 12v sense wire and another ground but the idea basically got ditched due to cost.
On the other hand, to draw more than 150w of power over a cable you need to use the 8pin connector according to PCI-SIG so everyone just slapped an extra ground cable in place of the 12v then everything is electrically compliant even if the 12v sense line isn't there and it all works.

Also, I should note that in that GTX 580 review; TPU does have information on their testing methodology and how they acquire their power figures if you wish to look into it. As well, the 304w figure is noted as being without the power limiter in place. Many high end cards for awhile now have had software limiters built in to make sure they don't go over the 300w figure but also have toggles to allow you to disable that. This way they can stay PCI-SIG compliant but also give enthusiasts the headroom to overclock and do as they please.

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the 8 pin got 3 +12V 3 wire and 2 sense.
the 6 pin got 2 +12V 2 wire and 1 sense.
some times you got 3, its out of spec, i dont know if the card actually use it.
http://nerdralph.blogspot.co.il/2016...tions.html?m=1
Last edited by none77; 05-20-2018 at 08:12 AM.

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Originally Posted by Tator Tot
As I said, the limit is "artificial" or "soft" and doesn't actually exist. The pins and wires can handle the extra current on the 6pin connector but way back PCI-SIG wanted to make an 8pin connector for higher draw components. Originally you were going to have a 12v sense wire and another ground but the idea basically got ditched due to cost.
On the other hand, to draw more than 150w of power over a cable you need to use the 8pin connector according to PCI-SIG so everyone just slapped an extra ground cable in place of the 12v then everything is electrically compliant even if the 12v sense line isn't there and it all works.

Also, I should note that in that GTX 580 review; TPU does have information on their testing methodology and how they acquire their power figures if you wish to look into it. As well, the 304w figure is noted as being without the power limiter in place. Many high end cards for awhile now have had software limiters built in to make sure they don't go over the 300w figure but also have toggles to allow you to disable that. This way they can stay PCI-SIG compliant but also give enthusiasts the headroom to overclock and do as they please.
Originally Posted by none77
the 8 pin got 3 +12V 3 wire and 2 sense.
the 6 pin got 2 +12V 2 wire and 1 sense.
some times you got 3, its out of spec, i dont know if the card actually use it.
http://nerdralph.blogspot.co.il/2016...tions.html?m=1
Thanks to you two, so that is what power target is for right?

And how to calculate power draw then? there's an article here but I think it is a bit old

http://www.jonnyguru.com/modules.php...ion&ndfaq_id=2

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If you want the aprox power draw just use a review.
to measure more correctly use 3 (maybe 1) clamps on the pcie cable and you got stack with the mobo slot that can go up to 75W.
if you want to be more precise you have to check the voltage to...
you can measure the power from the wall on stress with and without the gpu to know the approx watts, don't forget to multiple the efficient, that slightly change with current.
aris got a project i dont know if it's commercial.
https://www.tomshardware.com/reviews...tics,5481.html
Last edited by none77; 05-20-2018 at 10:58 AM.

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