wondering about total amps required to run 2 HD 5850's (i know it is old)

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blazingmatty

blazingmatty

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Nov 12, 2011
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basically i might be able to get another 5850 really cheap, like really really cheap (£20) but i won't be able to get a new power supply to go with it (i have a corsair CX600 v2, 46A +12v rail, i know it isn't the best) and according to the 'extreme power supply calculator' with the rest of my system (1090t, 16gb ram, 2 hard drives and 3 case fans all stock speeds with no intention of overclocking) and the 5850's it will pull a little less than 500w but it is the amps im worried about, will the 12v rail be able to keep up with the load or will it pop prematurely? also i am aware that a little under 500w is a little close really but if it will last till christmas or so then it should be fine. many thanks in advanced
 
Solution
bucknutty
I think you will be fine. You can solve the Wattage and amp questions by doing the math out. In the example below this looks like a close call on paper but i am using the highest possible draw for each part in reality you will not be able to tax every part of the computer at 100% like this.
HD5850 160w/12V=13.3A
1090t 125w/12v=10.4
Board+Drives+ Buffer 50w/12v=4A
So at 100% max usage this computer will draw up to 335Watts or 27 Amps.
If we add another 160w for the second HD5850 we are at 495w/12v=41 Amps.

In this example we see a 1090t and a HD5850 only pulling around 230 watts. As you can see my estimations were very high to account for overclocking and extra HDD and fans...
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bucknutty

bucknutty

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I think you will be fine. You can solve the Wattage and amp questions by doing the math out. In the example below this looks like a close call on paper but i am using the highest possible draw for each part in reality you will not be able to tax every part of the computer at 100% like this.
HD5850 160w/12V=13.3A
1090t 125w/12v=10.4
Board+Drives+ Buffer 50w/12v=4A
So at 100% max usage this computer will draw up to 335Watts or 27 Amps.
If we add another 160w for the second HD5850 we are at 495w/12v=41 Amps.

In this example we see a 1090t and a HD5850 only pulling around 230 watts. As you can see my estimations were very high to account for overclocking and extra HDD and fans.

http://www.tomshardware.com/reviews/amd-phenom-ii-x6-1090t-890fx,2613-13.html

 
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geofelt

geofelt

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Oct 9, 2006
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Here is the AMD recommendation.
It indicates that 600w with 4 6-pin pcie connectors will be needed.
http://www.amd.com/en-us/products/graphics/desktop/5000/5850#
Your psu has the wattage and amps to do the job in theory.
But, it only has two 6+2 pin leads.
A 6+2 lead is intended to deliver power to 8 pin pcie needs. It represents 75w more than a 6 pin lead.
So, in theory, using molex to 6 pin adapters should do the job.
I am always wary if a psu does not supply the leads you need.
Still, I think you will be OK. AMD and others overstate their requirements a bit to allow for cheap psu's that can not deliver advertised power.

Go ahead and try it.
If there is insufficient power, you might see artifacts and have to back off.
I see little chance of any real damage.
 
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blazingmatty

blazingmatty

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out of interest what amperage would a 5970 pull? i know it's an old card but im getting it cheap and is just about my only upgrade path, don't intend on doing any kind of overclocking and i have only 2 hard drives to power and whatnot, i may have enough for a better power supply down the line but not right away, so the question is really how long would the CX600 last i suppose
 
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