Is a EVGA P2 850W PSU enough to power a crossfired 290X & 390?

[Rob27shred]

Ok so I know there has been a ton of threads created on this subject & a 1000W PSU would be best for my situation. But I just upgraded my PSU to an EVGA P2 850w because I had no idea I'd be getting a 290X. I just happened to come across a great deal on the 290X I could not pass up.
My specs are
CPU: i7 6700K running at 4.5Ghz
Mobo: Gigabyte Z170XP-SLI (3 way crossfire & SLI capable)
GPUs: XFX DD core edition R9 390 8GB & MSI R9 290X gaming 4GB
PSU: EVGA SuperNOVA P2 850w (it has a single +12V rail that will supply up to 70.8A)
http://www.newegg.com/Product/Product.aspx?Item=N82E16817438056
RAM: 16GB (4GB X 4) Adata XPG DDR4 2800
Storage: 2 - 256GB 2.5" SSD, 1 - 3TB 3.5" 7200rpm HDD, 2 1TB 3.5" 7200rpm HDD
OD: LG blu ray drive
Fans - 9 total 120mm case fans
Being that my situation is a little more unique than trying to run 2 of the same cards in crossfire I figured I better ask you guys here at Tom's before I try it.

 

[rcald2000]

http://www.realhardtechx.com/index_archivos/Page362.htm

Even though the recommendations above are conservative, I still follow it. So in answer to your question, I wouldn't crossfire either of those GPUs with less than 1,000 watts. If you attempt to do it with the 850 watt unit, then you'll probably have less than 100 watts leeway when your system is under load. That would personally stress me out. By the way, I have the EVGA p2 850. Love it!

 

[rcald2000]

Upon deeper reflection, another option is that you can simply buy the two 290X or 390's and try on your P2 850. If it's underpowered then you could try to find a deal on NewEgg or elsewhere for a EVGA G2 1300. Even though it's gold efficiency, it achieves platinum efficiency around the 50% load level which will be equivalent to what your platinum efficiency 850 achieves at near full load. The G2 1300 is currently $200 on NewEgg but they have sales on it all the time. I've owned two G2 1300s, two G2 850s and one P2 850. I'm not looking to sell them though. Good luck.

 

[Rob27shred]

http://www.realhardtechx.com/index_archivos/Page362.htm

Even though the recommendations above are conservative, I still follow it. So in answer to your question, I wouldn't crossfire either of those GPUs with less than 1,000 watts. If you attempt to do it with the 850 watt unit, then you'll probably have less than 100 watts leeway when your system is under load. That would personally stress me out. By the way, I have the EVGA p2 850. Love it!

Yeah that is my problem, I absolutely love my 850P2 & literally got it under a week ago. I could return it to newegg but they will want to offer me 85% back since it is opened & not defective in anway... FML I wish I would've just went with a 1000 or 1200W when I got the 850 but at that time I did not have any plans on doing a crossfire setup & figured 850w was more than enough for my needs.

I guess for now I'll just switch out the 390 for the 290X since I'm gaming at 1080p (well downscaled from 1440p to 1080p thanks to VSR) & don't really need the full 8GB frame buffer. Then just get a 1000w or 1200w P2 when I can get a good deal on one of them. BTW thanks for the link, some good info there, definitely got bookmarked on my side!

 

[rcald2000]

@Rob27shred

I return things to NewEgg all the time without getting hit with a restocking fee. As long as you've owned it under a month and contact customer support (I like the chat) they should grant the full RMA. The only issue is that power supplies are heavy, so your shipping back might be pricey. You get the option of either shipping it back yourself, or they'll email you the shipping label and deduct it from your refund. You can see if they'll wave it. I "think" they have the power to, but I'm not 100% sure. If they grant the RMA then immediately order the PSU that you want and then ship back the P2 850 when you get the new PSU. I recommend that you request the RMA ASAP, and then you have options. You don't have to actually use the RMA. You can get it granted, try the P2 850 and if it works then you simply let the RMA auto-exipre. No big deal.

 

[Rob27shred]

Upon deeper reflection, another option is that you can simply buy the two 290X or 390's and try on your P2 850. If it's underpowered then you could try to find a deal on NewEgg or elsewhere for a EVGA G2 1300. Even though it's gold efficiency, it achieves platinum efficiency around the 50% load level which will be equivalent to what your platinum efficiency 850 achieves at near full load. The G2 1300 is currently $200 on NewEgg but they have sales on it all the time. I've owned two G2 1300s, two G2 850s and one P2 850. I'm not looking to sell them though. Good luck.

I was checking the 1300w G2 out also. I'm definitely open to a gold PSU since like you said will get roughly the same efficiency. The 850 P2 was only like $5 or $10 more than the G2 when I got it so I figured why not. Thanks for the advice bud!

 

[Rob27shred]

@Rob27shred

I return things to NewEgg all the time without getting hit with a restocking fee. As long as you've owned it under a month and contact customer support (I like the chat) they should grant the full RMA. The only issue is that power supplies are heavy, so your shipping back might be pricey. You get the option of either shipping it back yourself, or they'll email you the shipping label and deduct it from your refund. You can see if they'll wave it. I "think" they have the power to, but I'm not 100% sure. If they grant the RMA then immediately order the PSU that you want and then ship back the P2 850 when you get the new PSU. I recommend that you request the RMA ASAP, and then you have options. You don't have to actually use the RMA. You can get it granted, try the P2 850 and if it works then you simply let the RMA auto-exipre. No big deal.

I was gonna RMA it but decided to keep the 850P2. I am thinking of building another PC over the winter & it will come in handy if my plans work out! Also having a back up PSU is never a bad thing! I ended up ordering a Seasonic X series 1250W XM2 to power the crossfire setup. I really liked some of the EVGA models 1000W & over but newegg had the Seasonic on sale for $189 so that sealed the deal for me. Gonna have to find somewhere that sells sleeved cables for it though as I believe it comes with just straight up plastic sheathed cables.

 

[rcald2000]

That sounds awesome. Enjoy!