7970x2 hash drops problem

[areiks]

Hello,

I have a problem with my rig. Just testing 2x7970 configuration now (waiting for other mb to plug in more cards). I was trying bamt and xubuntu. I was also trying cgminer (many versions) and diablominter.

The problem is when i start mining on two cards the hash rate drops by a half. Eg. when i dont use command DISPLAY=:0 i have 650Mhash on one card. But when i use it i have about 300Mhash each (so overall it reamains the same).

What might be the problem? I tried many things, i have newest drivers on xubuntu now (from repository). Everything works fine, just hash rate drops.

Is it possible that my internet access is blocking me? I have just 0,5Mb connection to the internet and there is already one mining ring working (4x5830).

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[vasvla]

Do you have adequate PSU, anything less than real 650W is too weak for 2 X 7970, even more, depends partially on the rest of hardware. For example, I had almost no problem to put 6770 and 7770 on the same mb with full hash rate of both cards, 550W psu, old 939 mb and processor, dedicated for mining only. So I guess combo with same cards should be even easier to manage. Good luck!

[CryptoMer]

Hello,

I have a problem with my rig. Just testing 2x7970 configuration now (waiting for other mb to plug in more cards). I was trying bamt and xubuntu. I was also trying cgminer (many versions) and diablominter.

The problem is when i start mining on two cards the hash rate drops by a half. Eg. when i dont use command DISPLAY=:0 i have 650Mhash on one card. But when i use it i have about 300Mhash each (so overall it reamains the same).

What might be the problem? I tried many things, i have newest drivers on xubuntu now (from repository). Everything works fine, just hash rate drops.

Is it possible that my internet access is blocking me? I have just 0,5Mb connection to the internet and there is already one mining ring working (4x5830).

I am personally mining one of the alternate coins. However, I've got a very similar setup.
2x 7970's
1x 1000W PSU
Ubuntu 12.04 Desktop (I actually run xubuntu as my VNC X server
Catalyst 13.1 (with the included SDK)

I've not run into any significant problems, other than heat, with the configuration. I'd suggest you uninstall the drivers that were available from the stock repositories, and download directly from AMD's site.

[roflplatypus]

sounds like a temp problem. set the overheat temp for your miner to 120C. this way the hardware will do the throttling.

[miningdude]

Definitely sounds like your cores are heating up slowing the hash rate after awhile. The key is to keep that hot air constantly flowing away from the rig. Cold weather definitely helps of course, but most folks don't have that luxury this time of the year.