What % of a power supply do you want to use?

[Steel_Nugget]

I plan to SLI my GTX 670 FTW 4gb, and need to upgrade my PSU. So from some charts SLI gtx 670s would only need a 600w PSU. Here is what I'm going off. http://www.guru3d.com/articles_pages/geforce_gtx_670_2_and_3way_sli_review,4.html
So since the max power consumption is 433w with a CPU that requires more power 130w over my 84w. So would a 600w PSU do? The PSU would be 80+ certified. Also like the subject stated how much of the PSU is a safe amount? Using 90% or do you never want to go over 75-80%?
Thanks for your help!

 

[Suztera]

700W minimum. Scroll down the page from your link and it tells you the recommended wattage for power supply. You don't want to run your power supply at 90-100% of its rated wattage output.
The 80+ efficiency is talking about how efficient the psu is converting in converting AC power to DC. Example of a 80+ certified psu, if the pc actually takes 500W, it will pull 600W from the socket but 20% is lost as heat during the process of converting AC to DC.
This video explains it as well: https://www.youtube.com/watch?v=dOXTZizoknc

 

[Steel_Nugget]

700W minimum. Scroll down the page from your link and it tells you the recommended wattage for power supply. You don't want to run your power supply at 90-100% of its rated wattage output.
The 80+ efficiency is talking about how efficient the psu is converting in converting AC power to DC. Example of a 80+ certified psu, if the pc actually takes 500W, it will pull 600W but 20% is lost as heat.

If the PSU has 85% efficiency so 600w with 85% efficiency would be 510w, so I would be about 100w under the max output wouldn't I? So if I'm using a max of about 83% of the PSU would that be safe?

 

[MagicPants]

I like to use at most 80% of a power supply's capacity, however things have gotten more complicated since the 80+ rating system came out. Because PSU's are more efficient running around 80% max power, some platinum supplies are the exact same hardware as a copper supply, just rated for a lower wattage. So, in the case of high efficiency PSUs (gold or higher) it's generally okay to run them at 100% (or even higher, but read a review first, I suggest jonnyguru.com)

Also, I like semi-fanless designs (PSUs that run without fans at 30% or less capacity), so I make sure my system idles at below 30%.

 

[Suztera]

700W minimum. Scroll down the page from your link and it tells you the recommended wattage for power supply. You don't want to run your power supply at 90-100% of its rated wattage output.
The 80+ efficiency is talking about how efficient the psu is converting in converting AC power to DC. Example of a 80+ certified psu, if the pc actually takes 500W, it will pull 600W but 20% is lost as heat.

If the PSU has 85% efficiency so 600w with 85% efficiency would be 510w, so I would be about 100w under the max output wouldn't I? So if I'm using a max of about 83% of the PSU would that be safe?

No that not how it works.Lets take an actual product: Seasonic G550
Product link: http://www.seasonicusa.com/G-series-450-550-650.htm
The 550W is the rated wattage but that is not the maximum wattage the power supply can pull from the wall. 80+ gold is roughly 88% efficient. So the maximum wattage it can pull from the wall is 616 Watts but that is in AC form. The psu need to convert it to DC and it is 88% efficient in converting this so it give the pc components inside 550W.
And then of course you don't want to run a pc that takes 500W at load with a 550W power supply. It would be running at 90% load, not efficiency. The sweet spot is roughly 50-70% load.

 

[Steel_Nugget]

I like to use at most 80% of a power supply's capacity, however things have gotten more complicated since the 80+ rating system came out. Because PSU's are more efficient running around 80% max power, some platinum supplies are the exact same hardware as a copper supply, just rated for a lower wattage. So, in the case of high efficiency PSUs (gold or higher) it's generally okay to run them at 100% (or even higher, but read a review first, I suggest jonnyguru.com)

Also, I like semi-fanless designs (PSUs that run without fans at 30% or less capacity), so I make sure my system idles at below 30%.

700W minimum. Scroll down the page from your link and it tells you the recommended wattage for power supply. You don't want to run your power supply at 90-100% of its rated wattage output.
The 80+ efficiency is talking about how efficient the psu is converting in converting AC power to DC. Example of a 80+ certified psu, if the pc actually takes 500W, it will pull 600W but 20% is lost as heat.

If the PSU has 85% efficiency so 600w with 85% efficiency would be 510w, so I would be about 100w under the max output wouldn't I? So if I'm using a max of about 83% of the PSU would that be safe?

No that not how it works.Lets take an actual product: Seasonic G550
Product link: http://www.seasonicusa.com/G-series-450-550-650.htm
The 550W is the rated wattage but that is not the maximum wattage the power supply can pull from the wall. 80+ gold is roughly 88% efficient. So the maximum wattage it can pull from the wall is 616 Watts but that is in AC form. The psu need to convert it to DC and it is 88% efficient in converting this so it give the pc components inside 550W

This is one of the PSU I was looking at. http://www.newegg.com/Product/Product.aspx?Item=N82E16817139048&ignorebbr=1&cm_re=600w_power_supply-_-17-139-048-_-Product
Would it work? My PC.
EVGA GTX 670 FTW 4gb 1046mhz core 7608mhz mem: Intel I5 4440: 8gb (4gb*2) Adata
DDR3 1600: OCZ 500w 80+: MSI B85-G41

 

[Suztera]

You need 700W minimum power supply for SLI. At least 550W with single gpu.

The power supply you already have is enough for a GTX 670

This power supply would be better for 670 SLI.
http://pcpartpicker.com/part/antec-power-supply-hcg750m

 

[Steel_Nugget]

You need 700W minimum power supply for SLI. At least 550W with single gpu.

The power supply you already have is enough for a GTX 670

This power supply would be better for 670 SLI.
http://pcpartpicker.com/part/antec-power-supply-hcg750m

The problem I'm having is I'm on a limited budget. So I need the second GPU, a new PSU, and a new motherboard unless a GTX 670 can run on a PCIE 2.0 16x @ 4x slot. So if the power supply I listed would work I'd use it.

 

[Suztera]

You need 700W minimum power supply for SLI. At least 550W with single gpu.

The power supply you already have is enough for a GTX 670

This power supply would be better for 670 SLI.
http://pcpartpicker.com/part/antec-power-supply-hcg750m

The problem I'm having is I'm on a limited budget. So I need the second GPU, a new PSU, and a new motherboard unless a GTX 670 can run on a PCIE 2.0 16x @ 4x slot. So if the power supply I listed would work I'd use it.

As i suggested above, you need 750W minimum. You would run into more problems if you go with the CXM 600W
http://pcpartpicker.com/part/antec-power-supply-hcg750m

 

[Steel_Nugget]

You need 700W minimum power supply for SLI. At least 550W with single gpu.

The power supply you already have is enough for a GTX 670

This power supply would be better for 670 SLI.
http://pcpartpicker.com/part/antec-power-supply-hcg750m

The problem I'm having is I'm on a limited budget. So I need the second GPU, a new PSU, and a new motherboard unless a GTX 670 can run on a PCIE 2.0 16x @ 4x slot. So if the power supply I listed would work I'd use it.

As i suggested above, you need 750W minimum. You would run into more problems if you go with the CXM 600W
http://pcpartpicker.com/part/antec-power-supply-hcg750m

Just found this review, is this a trusted sight? http://www.guru3d.com/articles_pages/corsair_cx600m_psu_review,8.html

 

[Suztera]

I agree with what is said in the review. Especially the last sentence of this image from the link.
http://gyazo.com/548df3258d6a100e9d87399b74f7c35d

"We do recommend you to stick to one graphics cards with this PSU, but that can be a high-end one."

 

[ingtar33]

ok... someone once did the math, and i'll dig the work out, it's quite convincing but this is how it rolls...

PSUs are at their most efficient between 60%-85% power draw... i remember the work basically arguing that 66%-70% was ideal... The author then built a table explaining the "ideal" power supply sizes based on estimated system power draw in normal use. It's been my guiding light with questions like this... so here we go...

your 84W chip is a haswell cpu... assuming no overclocking for either it or that new 670 SLi setup, that's a 170W gpu normally, add in another and we're up to 424W on your system power draw; the rest of your system might (it won't but i like to be conservative) draw 100W, that's a total system power draw 524W

so the ideal psu for your setup would be...

524*1.4= 730W... since this whole formula is a "conservative" estimate, you can safely round DOWN... and say a 700W psu would be perfect size... and in a pinch a 650W would work too.

If you plan to overclock a 700W psu will be plenty enough to handle it, and if you don't plan to overclock this psu size will function at it's most efficient when under any normal load.


as to your other question... the % efficiency is how much power is wasted by your psu going from your wall to your computer... So a 80% efficient 700W psu will actually draw 875W from the wall when providing 700W of power to the computer. So ideally you want the most efficient psu you can get as that will save you $$ at the end of every month. It also will reduce heat in your system, as all that wasted energy turns into heat.

 

[Steel_Nugget]

ok... someone once did the math, and i'll dig the work out, it's quite convincing but this is how it rolls...

PSUs are at their most efficient between 60%-85% power draw... i remember the work basically arguing that 66%-70% was ideal... The author then built a table explaining the "ideal" power supply sizes based on estimated system power draw in normal use. It's been my guiding light with questions like this... so here we go...

your 84W chip is a haswell cpu... assuming no overclocking for either it or that new 670 SLi setup, that's a 170W gpu normally, add in another and we're up to 424W on your system power draw; the rest of your system might (it won't but i like to be conservative) draw 100W, that's a total system power draw 524W

so the ideal psu for your setup would be...

524*1.4= 730W... since this whole formula is a "conservative" estimate, you can safely round DOWN... and say a 700W psu would be perfect size... and in a pinch a 650W would work too.

If you plan to overclock, this psu will be plenty enough to handle it, and if you don't plan to overclock this psu size will function at it's most efficient when under any normal load.


as to your other question... the % efficiency is how much power is wasted by your psu going from your wall to your computer... So a 80% efficient 700W psu will actually draw 875W from the wall when providing 700W of power to the computer. So ideally you want the most efficient psu you can get as that will save you $$ at the end of every month. It also will reduce heat in your system, as all that wasted energy turns into heat.

How about this PSU? http://www.newegg.com/Product/Product.aspx?Item=N82E16817139048&ignorebbr=1&cm_re=600w_power_supply-_-17-139-048-_-Product

 

[ingtar33]

http://www.ncixus.com/products/?usaffiliateid=1000031504&sku=86285&vpn=HCG-750M

That psu would be ideal for your needs. I got my XFX psu from that vender, and have been using them for years... they aren't as fast with delivery as newegg, but they're a solid vender. If you perfer newegg, here is that same psu at newegg.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817371066

 

[Suztera]

The CXM 600W does not fit your requirements. It doesn't have the enough power connectors to power two GTX 670 in SLI. It only has two 6+2 pin PCIE connectors whilst GTX 670 SLi needs 4 6+2 pin PCIE connectors.

 

[Steel_Nugget]

The CXM 600W does not fit your requirements. It doesn't have the enough power connectors to power two GTX 670 in SLI. It only has two 6+2 pin PCIE connectors whilst GTX 670 SLi needs 4 6+2 pin PCIE connectors.

Actually the GTX 670s only require PCIE 6 pin power connectors.

 

[Steel_Nugget]

http://www.ncixus.com/products/?usaffiliateid=1000031504&sku=86285&vpn=HCG-750M

That psu would be ideal for your needs. I got my XFX psu from that vender, and have been using them for years... they aren't as fast with delivery as newegg, but they're a solid vender. If you perfer newegg, here is that same psu at newegg.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817371066

The problem I'm having is I need to get a SLI motherboard, PSU and another GPU for under $450, thats a problem because I'm limited in money as a 15 years old, and not being able to get a job for another year. So is it possible to get a motherboard and PSU for under $175 since I have found the GPU on ebay for $275?
Thanks for the help.
Btw the socket type is 1150, and I do have my specs listed on my profile.

 

[ingtar33]

oi... $275 for a 670 4gb on ebay? I'd keep looking on ebay for a better deal. i've seen those go for as low as $200 in the last few weeks (and i've been very temped as i'm also in the market for a new gpu... and of course i'm eyeing stuff on ebay).

I suggest you keep an eye on craigslist as well.

let me know what CPU you use and i'll see what we can squeeze together.

 

[k1114]

I don't know where you got efficiency is best at 60-85 (you don't even want to be getting to 85) but it's 50%. You can find the efficiency curve for just about any psu. For example here's the hcg 750m, notice it's best is at 40-50%. http://www.techpowerup.com/reviews/Antec/HCG-750M/6.html Here's the cx600m, this is a bit lower at 40%. http://www.techpowerup.com/reviews/Corsair/CX600M/6.html

 

[Steel_Nugget]

oi... $275 for a 670 4gb on ebay? I'd keep looking on ebay for a better deal. i've seen those go for as low as $200 in the last few weeks (and i've been very temped as i'm also in the market for a new gpu... and of course i'm eyeing stuff on ebay).

I suggest you keep an eye on craigslist as well.

let me know what CPU you use and i'll see what we can squeeze together.

The GPU is buy it now for $270, but bid for $180 so I'll see if I can get it for under $200. My CPU is an I5 4440, so not power hungry and can't be overclocked, that's why I was thinking I could squeeze it in on a 600w PSU. Also this review says they got 2 GTX 670s on a 600w. http://www.techpowerup.com/reviews/nvidia/geforce_gtx_670_sli/27.html
Here are the rest of my specs.
EVGA GTX 670 FTW 4gb 1046mhz core 7608mhz mem: Intel I5 4440: 8gb (4gb*2) Adata
DDR3 1600: OCZ 500w 80+: MSI B85-G41
And thanks!

 

[Suztera]

If you really want to risk your GTX 670s and your pc build with a 650W, here an option XFX 650W. IT has enough power connectors and is a much better quality than the CXM 600W.
http://pcpartpicker.com/part/xfx-power-supply-p1650snlb9

 

[Steel_Nugget]

If you really want to risk your GTX 670s and your pc build with a 650W, here an option XFX 650W. IT has enough power connectors and is a much better quality than the CXM 600W.
http://pcpartpicker.com/part/xfx-power-supply-p1650snlb9

I guess there is a risk, but shouldn't a PSU be able to handle under 80% load just fine?

 

[ingtar33]

I don't know where you got efficiency is best at 60-85 (you don't even want to be getting to 85) but it's 50%. You can find the efficiency curve for just about any psu. For example here's the hcg 750m, notice it's best is at 40-50%. http://www.techpowerup.com/reviews/Antec/HCG-750M/6.html Here's the cx600m, this is a bit lower at 40%. http://www.techpowerup.com/reviews/Corsair/CX600M/6.html

I didn't write it, but it's based on "average" system power draw. Granted a psu might be more efficient at 40-50% power draw, but it's basically the same efficiency out to 80%... and a computer doesn't draw 100% of it's possible max load... ever... even when heavily stressed it will rarely approach it's max load. The result was you built a computer with the idea of "max" non-overclock load being around 70% of the rated power of the psu. this would result in the highest possible psu efficiency MOST of the time the computer was on, AND it would give you enough extra power to let you overclock, AND have enough buffer for people who decide to add more hardware to their system down the road. It's a well argued formula that hasn't failed me yet..

oi... $275 for a 670 4gb on ebay? I'd keep looking on ebay for a better deal. i've seen those go for as low as $200 in the last few weeks (and i've been very temped as i'm also in the market for a new gpu... and of course i'm eyeing stuff on ebay).

I suggest you keep an eye on craigslist as well.

let me know what CPU you use and i'll see what we can squeeze together.

The GPU is buy it now for $270, but bid for $180 so I'll see if I can get it for under $200. My CPU is an I5 4440, so not power hungry and can't be overclocked, that's why I was thinking I could squeeze it in on a 600w PSU. Also this review says they got 2 GTX 670s on a 600w. http://www.techpowerup.com/reviews/nvidia/geforce_gtx_670_sli/27.html
Here are the rest of my specs.
EVGA GTX 670 FTW 4gb 1046mhz core 7608mhz mem: Intel I5 4440: 8gb (4gb*2) Adata
DDR3 1600: OCZ 500w 80+: MSI B85-G41
And thanks!

well, find an XFX psu~

If you really want to risk your GTX 670s and your pc build with a 650W, here an option XFX 650W. IT has enough power connectors and is a much better quality than the CXM 600W.
http://pcpartpicker.com/part/xfx-power-supply-p1650snlb9

yep. that's the best option

 

[k1114]

Saying to get your peak to 70 is not the same as saying the psu has the best eff at 70. You should aim for 60-70 peak to stay around the best eff around 50.

 

[ingtar33]

Saying to get your peak to 70 is not the same as saying the psu has the best eff at 70. You should aim for 60-70 peak to stay around the best eff around 50.

you're right. i used the wrong words. either way the principle still stands.