Periodically dropping hashrate

[Emrox]

Hi Folks,

so here's the thing: I mine with 4 cards: 2x 5850, 1x5870, 1x5970
Everything works as it's meant to be, except for one little thing:

Approximately every one or two minutes the hash rate of one card almost drops down to half of its normal speed.
The hash rate stays at half for several seconds (~10) and then hits its normal speed again.

At first I thought the 5850s where causing the problem since only those cards where dropping, but now from time to time the 5870 drops aswell.
Usually the drop is not randomly occuring on the affected cards, but occurs several times on the same card before another card drops.

The first time this problem occured was when I added the 5970.
So far I didn't find anything concerning the 5970 dropping other cards rates and I honestly don't think it is.
There are no additional programs running since I installed the 5970, just GUIminer and TrixXx.
All the cards are overclocked, but run stable and even resetting speeds to standard clocks didn't help.

I virtually checked everything I could imagine causing the problem and several hours of online research also didn't do the trick.


Hope I didn't miss anything, but if so, please let me know and I'll provide additional information.
Thanks in advance, every help is appreciated!

[tarion3]

Do you have your mining rig plugged into a power strip / surge protector of any kind?

The reason I ask is that I was experiencing this same issue with my setup. I read somewhere on the forum that the problem could possibly be due to a power-draw issue and that the power strip was not allowing proper power to the mining rig. (I had it full of other devices - monitor, printer, laptop charger, etc.) I immediately plugged my rig directly into the wall outlet (without the power strip) and the problem went away completely. So I'm thinking there is some validity to this. The sad part is that I'm in danger of frying my mining rig during a power spike / storm until I get a power strip capable of handling it.

[JoelKatz]

I would suspect heat.

[jragon23]

Your power supply could be unstable, use a voltage monitor like aida64.