Yes you can!
I'm currently at 750-800 watts with 3x HD7950.
All useless stuff from MB disabled (USB 3.0, sound...). I can even reduce the wattage by undervolting the CPU but not done yet.
If it can help you, here are my clocks and voltages (stable):
1050 / 1500 @ 1.012 V (77% ASIC quality in GPU-Z)
1050 / 1500 @ 1.018 V (75% ASIC quality in GPU-Z)
1050 / 1500 @ 1.056 V (66% ASIC quality in GPU-Z)
Mining around 1850-1900 Kh/s.
Topic: Help: 2X 7950 (MSI) - PSU??? 850W Enough if Undervolted? (Read 1337 times)
Your 850W is plenty for even a 3rd card. One of my rig is a 3x 7950 and draws 660W at the wall. The cards are undervolted to 1087.
720w from the wall for 3 7950s at 630kh with a 6core watercooled cpu 2 cards will be fine on that
1000W for 2 7950s?! Really? Whoever said that is a moron. If you're running 4 7950s, then I'd recommend 1000+W.
Count on 200W for each GPU. Then add ~100W for the system at idle, 200W if you're cranking your CPU (which shouldn't happen while mining). That's 600W. A lil wiggle room, and 650W is just fine.
I run 2x MSI 7950s with an AMD FX-8120 on a SeaSonic X-650 with no issues whatsoever.
Count on 200W for each GPU. Then add ~100W for the system at idle, 200W if you're cranking your CPU (which shouldn't happen while mining). That's 600W. A lil wiggle room, and 650W is just fine.
I run 2x MSI 7950s with an AMD FX-8120 on a SeaSonic X-650 with no issues whatsoever.
850W is enough for 2x7950+1x7970
Max watts is 400 for the 2 cards... it's all good
Wow, seriously? So I will be fine to run the 850w PSU with both 7950's even before I get around to undervolting them?
Also, thanks for everyone's feedback. Im glad I don't have to send the PSU back
Also, thanks for everyone's feedback. Im glad I don't have to send the PSU back
650W True Rated PSU is capable of handling the 2. 
I have 2-7950's with an X6 CPU on a 650 PSU, no issues.
650W True Rated PSU is capable of handling the 2.
You'll be fine.
Hello,
I am building a gaming rig that will also be able to mine some alt coins (CAP, BBQ, etc) and I just received my MSI 7950 Twin Frozr. I plan on getting a second one. WHen I plugged all of my specs and hardware intothe Newegg PSU calculator, it said I needed 829W. Then they have a "search PSU" button. Clicked it, found a Rosewill 850W, and ordered it.
But then later I saw a lot of people saying that for 2 X 7950's you need a minimum of 1000w PSU
I was planning on undervolting them too. So I am just wondering if 850w is going to be a sufficient PSU...especially since I will need to be playing some high-end games as well
Other specs:
AMD FX 8350
DVD-RW
RAM: DDR3 4 X 8gb (32gb)
Note: With just one card on New Egg's calculator it said it would be using 529W. I didnt think of it until later that an increase of 300w for an additional 7950 might not be correct
I am building a gaming rig that will also be able to mine some alt coins (CAP, BBQ, etc) and I just received my MSI 7950 Twin Frozr. I plan on getting a second one. WHen I plugged all of my specs and hardware intothe Newegg PSU calculator, it said I needed 829W. Then they have a "search PSU" button. Clicked it, found a Rosewill 850W, and ordered it.
But then later I saw a lot of people saying that for 2 X 7950's you need a minimum of 1000w PSU
I was planning on undervolting them too. So I am just wondering if 850w is going to be a sufficient PSU...especially since I will need to be playing some high-end games as well
Other specs:
AMD FX 8350
DVD-RW
RAM: DDR3 4 X 8gb (32gb)
Note: With just one card on New Egg's calculator it said it would be using 529W. I didnt think of it until later that an increase of 300w for an additional 7950 might not be correct
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