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7870's in Crossfire

Last response: in Components
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October 8, 2012 11:35:00 PM

Hello,
I've been planning on cross-firing two 7870's for a while now, and since my motherboard doesn't support SLI this is my only option for two cards.
My system specs are below:

CPU: Intel Core i5 3570K
Motherboard: AsRock H77 Pro 4-M
GPU: GTX 570
PSU: OCZ Technology 600 Watt Powersupply

Let me know if you want to know more, but yes will a 600 watt be enough for two 7870's. I'm planning to OC my CPU but I don't think its necessary for the GPU. I've seen on the website that it is a 600 watt minimum, but I want at least 100 watts headroom. And yes I know that total power wattage is not the most important, it is continuous power on the 12A Rail.

So let me know please!

Thanks

More about : 7870 crossfire

a c 142 ) Power supply
a c 403 V Motherboard
October 9, 2012 12:53:32 AM

HD 7870s have a max TDP of 175W. That works out to about 14.6A on the +12V rail per card. So you will need 29.2A on the +12V rail(s) just to supply the cards at max power. However, In real life, you'll probably never reach the TDP. Use a PSU calculator to estimate the total wattage needed for your entire system. http://www.thermaltake.outervision.com/ Then get a PSU of the necessary wattage with a +12V rail(s) that can handle the load. My hunch is that a 600W OCZ with about 50A available on the +12V rail(s) will be OK but minimal depending on the other devices in your system. Most folks go 750W or better.
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October 9, 2012 1:11:27 AM

clutchc said:
HD 7870s have a max TDP of 175W. That works out to about 14.6A on the +12V rail per card. So you will need 29.2A on the +12V rail(s) just to supply the cards at max power. However, In real life, you'll probably never reach the TDP. Use a PSU calculator to estimate the total wattage needed for your entire system. http://www.thermaltake.outervision.com/ Then get a PSU of the necessary wattage with a +12V rail(s) that can handle the load. My hunch is that a 600W OCZ with about 50A available on the +12V rail(s) will be OK but minimal depending on the other devices in your system. Most folks go 750W or better.


I did the whole system... but replaced the GTX 570 with two 7870's and it said 492 watts... Is that right?
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a c 142 ) Power supply
a c 403 V Motherboard
October 9, 2012 3:21:04 AM

sharpshooter_992 said:
I did the whole system... but replaced the GTX 570 with two 7870's and it said 492 watts... Is that right?

If you did the calc correctly, it should be. Remember, I was using a max/extreme situation when I listed the TDP. In normal use gaming, you will never reach that. And, speaking of the GTX 570, that older card uses far more power to achieve the same results as the HD 7870. http://www.hwcompare.com/12208/geforce-gtx-570-vs-radeo...
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October 9, 2012 1:44:02 PM

clutchc said:
If you did the calc correctly, it should be. Remember, I was using a max/extreme situation when I listed the TDP. In normal use gaming, you will never reach that. And, speaking of the GTX 570, that older card uses far more power to achieve the same results as the HD 7870. http://www.hwcompare.com/12208/geforce-gtx-570-vs-radeo...


Yes, I also did the max TDP. So will the 600 watt be enough for two 7870's?
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October 9, 2012 2:13:53 PM

sharpshooter_992 said:
Yes, I also did the max TDP. So will the 600 watt be enough for two 7870's?

Yes it will.
Trust us, your at Tom's.
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Best solution

a c 142 ) Power supply
a c 403 V Motherboard
October 9, 2012 3:21:44 PM

sharpshooter_992 said:
Yes, I also did the max TDP. So will the 600 watt be enough for two 7870's?

My feeling is yes. Not what I would recommend for someone looking to buy a new PSU for Xfire. But if you already have that size, use it. The 600W OCZ is a decent PSU and should work fine for you. If your system w/2 7870s calc'd out at 492W, you have plenty of headroom.
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October 9, 2012 10:05:31 PM

clutchc said:
My feeling is yes. Not what I would recommend for someone looking to buy a new PSU for Xfire. But if you already have that size, use it. The 600W OCZ is a decent PSU and should work fine for you. If your system w/2 7870s calc'd out at 492W, you have plenty of headroom.


Oh yes! More money left over for maybe a solid state drive!

Thanks!
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October 9, 2012 10:05:55 PM

Best answer selected by sharpshooter_992.
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