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  1. #1

    Can i Crossfire 2 7850 with my current 500W PSU?

    i've been thinking about buying 2 of these and crossfire, but is my PSU enough?

    http://www.newegg.com/Product/Produc...rmaster%20500w

  2. #2
    Herald of the Titans Saithes's Avatar
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    Assuming your PSU have a strong +12V Rail you most certainly can.

    Individual Power Consumption of just the card:

  3. #3
    Stood in the Fire ironik's Avatar
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    You would be pushing your PSU a bit too hard. Don't forget to account for CPU power consumption as well as other devices in the PC. I would recommend at the very least a 600W, but you can pick up a 750W for fairly cheap now, giving you a little room to upgrade your gfx in the future.

  4. #4
    Looking at this review of 7850 crossfire they have a power usage of 488W during load. http://www.tweaktown.com/reviews/479...w/index17.html

    The quality of your current PSU is questionable, it isn't even 80+ certified. It will probably work but it is risky.
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  5. #5
    so then should i be better off buying a single card
    such as 7870 or gtx 660?

  6. #6
    Yeah, for the same price as 2 7850 you can get 1 powerful card.
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  7. #7
    Herald of the Titans Saithes's Avatar
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    Quote Originally Posted by n0cturnal View Post
    Looking at this review of 7850 crossfire they have a power usage of 488W during load. http://www.tweaktown.com/reviews/479...w/index17.html

    The quality of your current PSU is questionable, it isn't even 80+ certified. It will probably work but it is risky.
    They ran a 3960X Extreme at 4.7GHz. The power usage of the CPU alone I guarantee is not comparable to the OP's. Subtract about 75-100 watts off of it.

  8. #8
    Quote Originally Posted by Saithes View Post
    They ran a 3960X Extreme at 4.7GHz. The power usage of the CPU alone I guarantee is not comparable to the OP's. Subtract about 75-100 watts off of it.
    He still has a low quality PSU so some extra headroom doesn't hurt.

    http://www.hardwaresecrets.com/artic...-Review/728/10

    It fails the noise and ripple test at 400W usage already.
    Last edited by n0cturnal; 2013-01-12 at 07:56 AM.
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  9. #9
    Herald of the Titans Saithes's Avatar
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    Quote Originally Posted by n0cturnal View Post
    He still has a low quality PSU so some extra headroom doesn't hurt.
    Doing the math here... Even assuming he has a 95w CPU.

    CPU: 95
    Graphics: 101 x 2
    Motherboard: 35
    RAM: 20
    Hard Drive: 15
    Various other components(Fans, SSDs, etc): 15

    Comes out to 382 watts. Most PSU's tend to run at their best efficiency around 50-75% load capacity. At 382, he is at 76.4% Load Capacity of the entire PSU.
    Last edited by Saithes; 2013-01-12 at 07:57 AM.

  10. #10
    Quote Originally Posted by Saithes View Post
    Doing the math here... Even assuming he has a 95w CPU.

    CPU: 95
    Graphics: 101 x 2
    Motherboard: 35
    RAM: 20
    Hard Drive: 15
    Various other components(Fans, SSDs, etc): 15

    Comes out to 382 watts. Most PSU's tend to run at their best efficiency around 50-75% load capacity. At 382, he is at 76.4% Load Capacity of the entire PSU.
    Yeah look at the review I posted above, also you don't know what kind of CPU he is running, he could just as well be running a 125W phenom or a FX series.
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  11. #11
    Herald of the Titans Saithes's Avatar
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    Quote Originally Posted by n0cturnal View Post
    Yeah look at the review I posted above, also you don't know what kind of CPU he is running, he could just as well be running a 125W phenom or a FX series.
    Even with 125w he is still fine.


    Edit: I do agree he is pushing, but he asked simply if it is enough and it is. Your review even says it can output the full 500w, the efficiency just goes down as it reaches 80% or more.

    Even your first review showing 488 watts proves its enough. They used a CPU that would be drawing like 225 watts with the overclock.
    Last edited by Saithes; 2013-01-12 at 08:06 AM.

  12. #12
    It can deliver 500W yes, but with ripple and noise way outside of the ATX standard. I wouldn't risk my hardware like that.

    This has nothing to do with efficiency or if the PSU can deliver enough power. The dangerously high ripple and noise values can destroy the components.

    If the ripple and noise is really high, it will do more than just corrupt data. It can shorten the life of attached hardware, or even fry it outright. I've seen several PCs destroyed when the PSU's capacitors went bad, which makes the ripple go through the roof.
    http://forums.hardwaresecrets.com/sh...25&postcount=2
    Last edited by n0cturnal; 2013-01-12 at 08:11 AM.
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  13. #13
    Quote Originally Posted by Elian View Post
    so then should i be better off buying a single card
    such as 7870 or gtx 660?
    Yes. Buying two weak cards for Crossfire or SLI will always end in tears. Dual card gaming has so many problems you should never do it unless you actually need the power of two high end cards to run triple screen gaming monsters.
    Never going to log into this garbage forum again as long as calling obvious troll obvious troll is the easiest way to get banned.
    Trolling should be.

  14. #14
    Stood in the Fire ironik's Avatar
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    Quote Originally Posted by vesseblah View Post
    Yes. Buying two weak cards for Crossfire or SLI will always end in tears. Dual card gaming has so many problems you should never do it unless you actually need the power of two high end cards to run triple screen gaming monsters.
    Or one GIANT screen. :-)

  15. #15
    Most the power consumption there comes from the 12V rail. It's pushing it with a 500W low quality PSU and I would NOT recommend it under any circumstance. 400-500W PSU is enough to run most systems with 1 video card. When we're talking two video cards we're talking 600W+ PSU's based on the quality of the manufacturer. For a "lesser brand" I would recommend adding 50% wattage above what you need in order to account for noice, ripple and generally low wattage out from the 12V rails.

    TL;DR
    Don't even think about it. Worst case scenario you will not only damage your PSU but also the rest of your PC. Get a new PSU or a powerful single card solution. The latter is the best option anyway unless you want to live in Crossfire's microstutter heaven. 7970GHZ will outperform those 7850's in actual game performance anyway.

  16. #16
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    I love when your "TL;DR" is almost as long as your first paragraph Lemmiwink

    It is possible you could but it might be cutting it real close but either way you really should just be looking at a stronger single GPU.
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  17. #17
    Watts is almost irrelevant, but yes 500 watts is more than enough assuming you just have a HDD and no extra lights and shit hooked up.

    I have no idea why manufacturers rate PSU's in watts when AMPS is the far more important factor. You are going to want around 45 amps for crossfire 7850's.

    But like other people have stated, get crossfire out of your head, unless you want more problems than it is worth. Sure its cool looking and crossfire is a sexy term, but there are games out there that play worse with crossfire than with a single card. Crossfire also does not work with windowed mode, meaning if you play a game that supports windowed fullscreen (the best mode) you wont be able to take advantage of it because of crossfire.

  18. #18
    Mechagnome Punisher's Avatar
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    You could, but I would recommand to get a powerfuller PSU, since AMD recommand a 600W PSU for 7850 in Crossfire

  19. #19
    I have no idea why manufacturers rate PSU's in watts when AMPS is the far more important factor.
    The wattage of the unit is from the maximum load possible. This includes the 3.3V and 5V rails as well as the 12V rail(s).

    So they provide the 3.3 and 5V rails with lots of amps (maybe 30-40 each (99-132 and 150-200 respectively) and the 12V rail gets maybe 15W (180W) on a "500W power supply".

    So they can advertise a crappy unit as a good one, so long as the customer doesn't know to look at the label. And lets face it, put yourself in the shoes of somebody with a budget and no knowledge of computer hardware. They see a "500W PSU" for 25 bucks, and a "500W PSU" for 80 bucks. Which would they buy?
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  20. #20
    what if i try underclocking both until i get a better psu?

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