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New system, new PSU : 3 questions

Last response: in Components
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January 7, 2012 8:34:45 PM

This is my new system i'm buying :

Intel Core i7-2600K
XFX HD-697A-CNFC Radeon HD 6970
MSI Z68A-GD65 (G3)
Cooler Master HAF with 3 large fans
Aerocool Touch 2000 front LCD screen
2x cold cathode lights
1x Samsung 128gb SSD
2x SATA hdd's
1x LG DVD Burner

I was told that my 400w Seasonic 80+gold power supply won't be enough :( 


So if i'm to buy a new power supply, i'll buy something overkill that would be enough to power up two of these cards in crossfire for a future upgrade, which led me to ask a few questions :

- How many watts would i need for dual XFX HD-697A-CNFC Radeon HD 6970 in crossfire mode ? Considering i'll be buying 80 plus GOLD psu

- What does "crossfire certified" and "crossfire ready" means ? I noticed a lot of PSU have these labels but people are running crossfire with non-certified PSU. Should i buy certified or not certified ?

- Let's say i buy a 1250 watts PSU. Will it use 1250 watts all the time (which would cost a lot of electricity) even if my system only consume, say 600 watts ?

thanks !!

More about : system psu questions

a b ) Power supply
January 7, 2012 9:20:00 PM

for 2 6950's stock a good 650 watt will do it if you shooting for high clocks 750 will be more then adequate

that certification is just marketing bs dont pay attention to it

your psu will only provide what your system needs if it needs 300 watts it will use 300 watts irrespective it your psu is rated at 400,500 or even a million watts your pc will still be pulling just the amount needed

getting an over powered psu for a lower wattage system has some lower wattage efficiency implications but its negligible with a good quality psu
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January 7, 2012 9:20:19 PM

ungovernable said:

- How many watts would i need for dual XFX HD-697A-CNFC Radeon HD 6970 in crossfire mode ? Considering i'll be buying 80 plus GOLD psu


According to the MSI power calculator you need at least 550 watts, and that doesn't include the lights. Thats the absolute minimum, so getting a somewhat more powerful one, say 600 or 650 watts should be fine according to MSI.

ungovernable said:

- What does "crossfire certified" and "crossfire ready" means ? I noticed a lot of PSU have these labels but people are running crossfire with non-certified PSU. Should i buy certified or not certified ?


The label just means that the manufacturer got the PSU tested in compliance with AMD's requirements. A non-certified one could be just as good as a certified one and may also be cheaper. What you choose depends on what brands you trust.

ungovernable said:

- Let's say i buy a 1250 watts PSU. Will it use 1250 watts all the time (which would cost a lot of electricity) even if my system only consume, say 600 watts ?


No. The 1250 watts refers to either the peak power that can be supplied or the maximum continuous power. Just check because, if it refers to the peak power, which can only be supplied for a short while, then the maximum continuous power will be lower. The figure you really care about is the maximum continuous power.
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January 7, 2012 9:34:52 PM

obsidian86 said:
for 2 6950's stock a good 650 watt will do it if you shooting for high clocks 750 will be more then adequate


I thought there was something odd about the figures from the MSI power calculator. I've since checked on the Thermaltake PSU calculator, which says you'll need about 850 watts for 2 6970s in crossfire if the PSU is expected to last for a few years. I'm inclined to believe the Thermaltake site over MSI.

You can choose different values for the capacitor aging on the Thermaltake site. These values are based on how often you want to use the PC and how long you want to keep the PSU. Basically, anything from 750 watts upwards should be fine.
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January 7, 2012 9:54:02 PM

Thanks for the infos guys

Well according to that MSI Power Calculator, i would need only 350 watts for my whole system with only 1 xfi graphic card... So in theory i should be fine with my Seasonic 80+ gold PSU.... Then why newegg says that XFI graphic card needs at least 550 watts ??
http://www.newegg.ca/Product/Product.aspx?Item=N82E1681...

if i can avoid buying a new PSU i would really like to stick with this Seasonic PSU as i paid almost $200 for it only a few months ago
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a b ) Power supply
January 7, 2012 10:15:22 PM

it should be fine

here is a chart showing maximum card power draw under furmark gaming it draws bout 2/3 max of this

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January 7, 2012 10:34:26 PM

Thanks for the chart, very useful

but according to it, the maximum power draw is 283W

my CPU is 95W, 50W for HDD, 20W for DVD, 20W for ram

so that's 468W and not counting my LCD front panel, SSD and cold cathodes

i guess my seasonic 400W won't be enough :( 
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a b ) Power supply
January 8, 2012 12:55:57 AM

ungovernable said:
Thanks for the chart, very useful

but according to it, the maximum power draw is 283W

my CPU is 95W, 50W for HDD, 20W for DVD, 20W for ram

so that's 468W and not counting my LCD front panel, SSD and cold cathodes

i guess my seasonic 400W won't be enough :( 


but thats if you load everything to 100% which is near impossible outside of competitive benching

the first chart was furmark loads this is gaming loads



you have a good psu with all the protections needed and you can load the psu to 450 watts before they kick in and even if its overloaded so so far it will turn off before anything serious happends so you are safe
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January 8, 2012 1:12:48 AM

Oh i see... Thanks a lot !

I'll give it a try before buying a new PSU then

When i receive my pieces, is there some kind of application to run a "stress test" so i can load my CPU and GPU to the maximum watts and see how my PSU handle it ?
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a b ) Power supply
January 8, 2012 1:25:26 AM

occt is a fairly complete tool for stress testing

http://downloads.guru3d.com/OCCT-(OverClock-Checking-Tool)-3.0.0-download-1880.html

also look into getting a kill-a-watt meter

it keeps tabs on the amount of power your drawing from the wall

average draw for a gold rated psu will be 10% more then whats being pulled from the psu
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January 8, 2012 2:01:06 AM

Thanks to both of you guys !! You were very helpful... i wish i could select two best answers
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a b ) Power supply
January 8, 2012 2:43:13 AM

Quote 50W for HDD, 20W for DVD end quote.

PSUs and dvd drives are only around 10->12 watts.

My I5-2500k w/2 SSDs, 1 HDD, 1 Blu-ray rom/dvd drive, 16 gigs ram, 1 6870 GPU -Max power running furmark is 350 Watts at wall.
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