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Good PSU for AMD RADEON HD 7870 OC Crossfire - Page 2

post #11 of 12
Quote:
Originally Posted by Abyssic View Post

Hey guys ive got the same question as the first one but with a closer look on amperage. amd recommends 34amps for one 7870. does that mean im gonna need 68amps (+OC) for two of them? please help.

 

All that would be needed is a quality-made 520-550W power supply with a +12V capacity of about 40A (480W).  A +12V capacity of 68A is 816W, and this is something that would be found in a quality 850W PSU, but it's not possible for the 2nd card to draw as much power as the main card because the 2nd card only adds about a 50% increase in GPU processing power.  However, the main card isn't able to pull 34A;  that's 408W which is a +12V capacity of some decent 430W power supplies.  AMD is just saying that enough room must be left over on the +12V for the rest of the parts in the system that get their power from the +12V.

 

One 7870 alone will pull up to about 130W which is about 10A on the +12V (which leaves more room on the +12V than anyone would ever need).  Adding a 2nd 7870 will only pull an extra 60-70W at the most which is 5-6A.  Well, 16A is 192W.  If we just go ahead and say that two 7870s will pull up to 20A together, then that is still only 240W.  Add 77W for the i5-3450 and then add about 150W for idling, and it comes out to 467W under the most extreme conditions possible.  If we only add the 192W instead of 240W, then it comes out to be 419W.

 

Now, I don't know anything about the 530W Thermaltake Hamburg yet, so I can only hope that it's at least comparable to their Toughpower series.

 

By the way, change your avatar as quickly as you can because OCN's rules are strictly enforced and I'd hate to see you get busted for that.


Edited by TwoCables - 10/25/12 at 3:12pm
    
CPUMotherboardGraphicsRAM
i5-2500K @ 4.5GHz (1.384 - 1.392V) ASUS P8P67 EVO B3 (UEFI ver. 1850) GTX 780 ASUS DirectCU II (1228 / 6300, 1.180V) G.SKILL Ripjaws X 8GB (2 x 4GB) 1866MHz, CL9 
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250 GB Samsung 840 EVO (C:) 250 GB Samsung 840 EVO (D:) Samsung SH-S243N 24x DVD Burner Samsung SH-S203N 20X DVD Burner 
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CPUMotherboardGraphicsRAM
i5-2500K @ 4.5GHz (1.384 - 1.392V) ASUS P8P67 EVO B3 (UEFI ver. 1850) GTX 780 ASUS DirectCU II (1228 / 6300, 1.180V) G.SKILL Ripjaws X 8GB (2 x 4GB) 1866MHz, CL9 
Hard DriveHard DriveOptical DriveOptical Drive
250 GB Samsung 840 EVO (C:) 250 GB Samsung 840 EVO (D:) Samsung SH-S243N 24x DVD Burner Samsung SH-S203N 20X DVD Burner 
CoolingOSMonitorKeyboard
Thermaltake Frio Win 7 Home Premium x64 SP1 Retail Samsung 2253BW (1680 x 1050) Filco Majestouch 104-key Cherry MX Blues w/NKRO 
PowerCaseMouseMouse Pad
Corsair HX650 (Bronze, ordered on 12-12-2009) CM 690 Microsoft Intellimouse Optical (not 1.1A) Basic, but premium round 
AudioOther
X-Fi Titanium HD Altec Lansing VS4121 (2.1 speaker system) 
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Reply
post #12 of 12
Seasonic X-660 gold, 7870 only draws 180 watts not 34 amps more like 15 at TDP. One of the best brands out there. thumb.gif
Double Vision
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Double Vision
(19 items)
 

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CPUMotherboardGraphicsRAM
Ivy Bridge 3770K with IHS removed Asus Max V gene Gigabyte Windforce OC 670 X 2 G Skills Trident X 2 x 4gig 
Hard DriveHard DriveOptical DriveCooling
Crucial M4 SSD Samsung Sony 24X Tfc Monsta 420 and Tfc Xchanger 360 
CoolingCoolingCoolingCooling
Rp 452 res with 2 x D5 varios and DD Cp pro for... Arqtic dual TEC chiller with 2-400watt Qmax tec... Ek supreme Cpu block with modified plate and 2 ... 9 x CM 120 mm R4 fans-1 x 140 Bitfenix Pro fan ... 
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7 Ultimate Phillips 234 23 inch Logitech G110 Seasonic X-1250 
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Dual CM Haf 922`s CM Sentinel Advance 2 Big 
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