Coolermaster 720w for 2 x 7950 not enough?

G

Guest

Guest
Coolermaster M2 Silent Pro 720W
Amd Athlon X3 450
Asrock 970 Extreme 4
Corsair 4 Gb ram
Kingston Hyperx 120 GB ssd
MSI R7950 Twin Frozr III 3GB ( 2 x)

I use this rig to mine litecoins. But I can only use one 7950. When I put them both to work the screen goes black after some minutes. Yet the computer doesn't reboot or shutdown, the fans keep spinning at full speed.. Very weird.


Could this that my psu isn't powerfull enough? Or maybe the gpu's shutdown becquse of the heat? Although they don't get hotter than 80 degrees celcius.
 
Your power supply unit is more than sufficient to handle two Radeon HD 7950 graphics cards in 2-way CrossFireX mode.

As for temperatures techPowerUp.com measured the following during their review of the MSI HD 7950 Twin Frozr III 3GB:

Idle: 32°C
Load: 59°C
Load + OC: 63°C

Your problem seems more like application incompatibility with CrossFireX mode.
 

Vimy

Honorable
Apr 7, 2013
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10,510
I don't use crossfire, that's not needed to mine litecoins.
I can use both cards perfectly but not at the same time.
One card at 100 % load hovers around 69 °C, when I start the second one the first card temps climb to 75, 76 °C
Then between 2 / 20 minutes pass before the screen goes black. Or more rarely the screen doesn't go black but everything freezes.

I read that coolmaster psu's aren't as powerfull as the specs say and a 700 watt is really a 650 watt or 600. (should have read that before I bought them.. oh well)
Maybe that's the problem?

Edit:
This is my setup: http://imgur.com/iM5XoIw
The highest card is 100 % load at 69 °C
Then when I turn on the card below this rises steadily to 79 °C.
The card below hovers around 65 °C
I think the lowest card heats up the air above it so suddenly the highest card gets much warmer air to cool.

So I'm starting to think the first card shuts off when it reaches 80 °C. A failsafe maybe?
But if that's the case why doesn't the second card also give a black screen when I switch the monitor cable?



 

Vimy

Honorable
Apr 7, 2013
2
0
10,510
Update:
So it seems heat was the problem. I put a big ass fan next to my pc. A regular fan, not a computer one and voila, problem solved.
The two cards have being working fine for over an hour with 100 % load! highest card 63°c, lowest 60°c, haha, what a difference with before! :p

Would it be possible to override the 80°C cutoff point? I would like to change it to 90°C or something like that.
 


Maybe it's time to try water cooling.