Title: PSU needed for 3 x HD 7970 Post by: surphactone on May 31, 2013, 05:11:30 PM Hi
which PSU should i buy to run 3 x 7970 , how many watt ? Title: Re: PSU needed for 3 x HD 7970 Post by: fflewddur on May 31, 2013, 06:10:10 PM I'm running four with a Corsair 1200AX, but you could get away with less. I'd recommend the Corsair AX860i; it's 860 watts and super efficient. Mine is powering two 7950s and never draws more than 415 watts... should be plenty of headroom for three 7970s, especially if you undervolt them a bit.
Title: Re: PSU needed for 3 x HD 7970 Post by: Kaepora on May 31, 2013, 06:22:46 PM Hi which PSU should i buy to run 3 x 7970 , how many watt ? 850 watts minimum, if you do go with an 850 watt it better be a quality one with some nice beefy rails. Title: Re: PSU needed for 3 x HD 7970 Post by: diskodasa on May 31, 2013, 06:26:03 PM At least 1500W because of this http://www.amd.com/us/products/desktop/graphics/7000/7970/Pages/radeon-7970.aspx#2
Title: Re: PSU needed for 3 x HD 7970 Post by: Kaepora on May 31, 2013, 07:01:12 PM At least 1500W because of this http://www.amd.com/us/products/desktop/graphics/7000/7970/Pages/radeon-7970.aspx#2 Whoa there buddy 1500w is excessive even a 1000w power supply is more than enough.Title: Re: PSU needed for 3 x HD 7970 Post by: fflewddur on May 31, 2013, 07:35:06 PM At least 1500W because of this http://www.amd.com/us/products/desktop/graphics/7000/7970/Pages/radeon-7970.aspx#2 There's absolutely no need for a 1500 watt PSU to run three 7970s. Around 850 will work, but power supplies are a great example of getting what (watt?) you pay for. Just because a PSU draws 850 watts from the wall doesn't mean it converts all of that into usable DC electricity. A cheap one may only only work at 70% efficiency, which leaves you with ~595 watts; a better (read: more expensive) 850 watt PSU should work around 90% efficiency, and give you a clean 760 watts, which is plenty to power three 7970s. Title: Re: PSU needed for 3 x HD 7970 Post by: surphactone on May 31, 2013, 09:44:20 PM thanks all ;D
i will go for a good 850 watts one :P Title: Re: PSU needed for 3 x HD 7970 Post by: diskodasa on June 06, 2013, 12:46:51 PM thanks all ;D i will go for a good 850 watts one :P Any news on 850W PSU with 3 gpu-s? Is it working? Stable...? Title: Re: PSU needed for 3 x HD 7970 Post by: dracula3 on June 06, 2013, 02:29:21 PM I'm running four with a Corsair 1200AX, but you could get away with less. I'd recommend the Corsair AX860i; it's 860 watts and super efficient. Mine is powering two 7950s and never draws more than 415 watts... should be plenty of headroom for three 7970s, especially if you undervolt them a bit. Hi, about these 415 watts how did you achieve that? It seems very good, considering each 7950 as 200W. Is this from wall - do you use some kill-a-watt? Or is this number from Corsair software provided with AX860i? Title: Re: PSU needed for 3 x HD 7970 Post by: Alexander The Great on June 06, 2013, 02:33:31 PM 800-900 watts is perfect.
Title: Re: PSU needed for 3 x HD 7970 Post by: artos on June 06, 2013, 02:37:35 PM PSUs are most efficient at the 80-90% range. So you'll want a 800-850W PSU.
Title: Re: PSU needed for 3 x HD 7970 Post by: Alexander The Great on June 06, 2013, 02:40:27 PM PSUs are most efficient at the 80-90% range. So you'll want a 800-850W PSU. Yes I agree Title: Re: PSU needed for 3 x HD 7970 Post by: JohanS on June 06, 2013, 03:04:42 PM thanks all ;D i will go for a good 850 watts one :P Nice! GL Title: Re: PSU needed for 3 x HD 7970 Post by: foxhole on June 06, 2013, 03:26:52 PM any one of them will do the trick
Title: Re: PSU needed for 3 x HD 7970 Post by: Eva Braun on June 06, 2013, 03:49:45 PM yes anyone of those will do the trick
Title: Re: PSU needed for 3 x HD 7970 Post by: skl1 on June 06, 2013, 04:01:18 PM 800W of 12v min for sha, and ~900+ of 12v for scrypt
Title: Re: PSU needed for 3 x HD 7970 Post by: Eva Braun on June 06, 2013, 04:07:47 PM 800W of 12v min for sha, and ~900+ of 12v for scrypt I own a 800W, works like a charm Title: Re: PSU needed for 3 x HD 7970 Post by: lbr on June 06, 2013, 05:06:02 PM At least 1500W because of this http://www.amd.com/us/products/desktop/graphics/7000/7970/Pages/radeon-7970.aspx#2 AMD publishes PSU requirements like this because if they said PSU must be able to deliver ~20A on +12V rail nobody would understand what they mean ; ) Also because PSU manufacturers often lie about their PSU specs. I'm running 3x7950 + 2x6950 mining LTC with Enermax 1250W works fine. One of 7950 was even using ~320W until I've noticed it and lowered voltage. PSU = Power Supply Unit ; ) Title: Re: PSU needed for 3 x HD 7970 Post by: https on June 06, 2013, 05:15:07 PM sorry but what does PSU stand for? Power supply unit Title: Re: PSU needed for 3 x HD 7970 Post by: namecoin on June 06, 2013, 05:21:16 PM why does scrypt requires more power than sha-256? because we need more ram for scrypt? thank you. ???
800W of 12v min for sha, and ~900+ of 12v for scrypt Title: Re: PSU needed for 3 x HD 7970 Post by: bublus7 on June 06, 2013, 07:42:01 PM I guess the figures are accurate.
And yes, more ram should be the reason for different power requirements. Title: Re: PSU needed for 3 x HD 7970 Post by: BloodOnSunday on June 06, 2013, 09:35:29 PM 850-1000W :D
Title: Re: PSU needed for 3 x HD 7970 Post by: fforforest on June 06, 2013, 09:36:28 PM Around 1000w should be OK. Preferably Gold certified.
Title: Re: PSU needed for 3 x HD 7970 Post by: thegamekind on June 06, 2013, 11:07:31 PM 850 is enough and i would use corsair just preference ::)
Title: Re: PSU needed for 3 x HD 7970 Post by: PenguinWriter on June 06, 2013, 11:18:13 PM You could also just get a lower wattage Gold (which are usually cheaper) and buy a PSU adapter so both power supplies turn on at the same time. Else for 3x 7970s I'd suggest at least a 1400W Gold to give you some headroom since most PSUs are not rated for their 100% capacity for more than a few seconds.
Title: Re: PSU needed for 3 x HD 7970 Post by: powerlevel on June 07, 2013, 12:42:36 AM 1200W should be safe.
Title: Re: PSU needed for 3 x HD 7970 Post by: Alexander The Great on June 07, 2013, 01:22:13 AM Corsair has great products
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