2 cards - One throttles when the other starts?

[alexdrans]

I have two 5870s and I'm having troubles getting them running together. When the second miner is running on its own it runs fine, but once I start the first miner the MHash/s of the second card drops to about 15. This only happened when I reinstalled Ubuntu 11.04 for a client and I can't figure out why it's doing this.

Does anyone have any idea?

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[anthony.selby]

Are you sure your changing the device tag ?

[drgr33n]

You got them crossfired ? If so don't run them as single cards. If not I'm not sure maybe its a power issue ? I've had machines that have done that just before the power supply packed up.

[alexdrans]

Yeah, one is clearly --device=1 and the other is --device=2

Device 2 works fine on its own, but soon as device 1 starts device 2 goes REALLY slow, almost as if device 1 is stealing from it.

Both cards worked fine in Ubuntu 11.04 before I reinstalled the OS to have everything fresh for a client. Before I just had both cards in the system without a CF bridge and I could address them individually. The system still recognises 2 cards and they both work because I can get them to work one at a time but not together.

What's wrong here :S

[MiningMonitor]

For me at least, after a lot of fiddling, I found a solution to the rate hoping problem.

Im Using Linuxcoin 0.2a with a machine that has 2x5830 ( technically 3 machines, but all are running linux coin with identical hardware )

The problem is the aggression setting on the first card.  While you lose a touch of speed off the first card, the second becomes rock steady.

Using pheonix I do something like:

Card 1 ( primary ):
DEVICE=0 AGGRESSION=7 FASTLOOPS=true

Card 2 ( primary ):
DEVICE=1 AGGRESSION=11 FASTLOOPS=false

Make sure you add in all your other standard options

This gives me 298mh/s on card one and 301 on card2 ... both rock steady and shares submitted / accepted averages out to be almost exactly the same ( indicating similar hashing rates With identical overclocking settings ( 1010mhz, 300mhz ram, 1.125v ))