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3870 Power Draw Question

post #1 of 9
Thread Starter 
I am really not sure how all of this works so here is my question.

I have 3 Sapphire Toxic 3870s in CrossfireX. I am trying to determine how much power these things draw but I am just not sure how to calculate this. If I look at this link it shows the idle, average, and max power usage for a single card. If I look at those numbers with the card at peak it is drawing 226 watts of power. If I have three, surely they would not draw 678 watts of power total. Isn't there some sort of factor that determines the total power draw with multiple cards?
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The Ark
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post #2 of 9
That's the total watts for the test machine. The power draw of single 3870 (reference card) is 105W.
post #3 of 9
Thread Starter 
Quote:
Originally Posted by linskingdom View Post
That's the total watts for the test machine. The power draw of single 3870 (reference card) is 105W.
Thanks I must have looked over that part. Just trying to search for an answer and ran across that.

Is that 105W idle or load?
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post #4 of 9
load of course.
post #5 of 9
X-bit's independent testing of the reference 3870 showed a real power draw of only 80-85W under full load, very similar to the 8800GT.
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mitx
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post #6 of 9
105w is assuming full 100% load with no overclocking or voltage mods.
post #7 of 9
Thread Starter 
Ok now lets say that I have three of these. Is there a way to calculate the total wattage all three combined would need at 100% load (stock) to run. I am under the impression through various searches (alhtough I have found nothing concrete) that indicates that they all do not use the full wattage when in crossfire. In other words I am assuming that with three cards it would not be 105 x 3 = 315W, correct?
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The Ark
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WD 1TB Green Lite-On 20x LH-20A1L ZALMAN CNPS9900MAX-R 135mm Windows 8.1 Pro x64 
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post #8 of 9
Well you have to take into account the fact that crossfire, while better than sli still does not scale enough to use all 3 GPUs to their full capacity. Figure in a few more watts each if you're overclocking. But yes I'd say ~300-350w for the cards alone full load.

So no, the 2nd and 3rd cards will probably not see 100% utilization, therefore not consume that full 105w.
post #9 of 9
Thread Starter 
Thanks!

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The Ark
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CPUMotherboardGraphicsRAM
AMD FX-8350 ASUS M5A99FX PRO R2.0 PowerColor AX7870 2GBD5-M2DH G.SKILL Ripjaws 4GB DDR3 1600 
RAMHard DriveHard DriveHard Drive
CORSAIR XMS 8GB DDR3 1600 OCZ Vertex 4 VTX4-25SAT3-256G WD 750GB Black WD 500GB Black 
Hard DriveOptical DriveCoolingOS
WD 1TB Green Lite-On 20x LH-20A1L ZALMAN CNPS9900MAX-R 135mm Windows 8.1 Pro x64 
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HP w2007 HP w2007 Logitech MK520 Ultra X3 1000W 
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