Bitcoin Forum

I have three 5830s and what I'm finding is that the 1st card (gpu0) mines the fastest, the second one about 20 Mhs less, and the third one about 20Mhs less than the second one. Right now they are at 300, 280 and 260.

System:
1000W PSU
Sempron 145
Asus m5a99x evo
4GB ram
Windows 7 + GUI miner using poclbm

Same situation with ubuntu

I had something similar when running 4 6990s, I noticed the speed would drop about 100mhash/s per core once they got going, I found the problem to be that the power supplies were not giving enough power.

What are the cards clocked at?

The PSU is definitely not your problem (unless it's faulty).

I have the same issue with 6970s. Both cards are clocked exactly the same ... in fact I load both cards up with the same profile from AMDOverdriveControl. But GPU0 load stays consistently at 99% whereas GPU1 goes up and down.

975MHz across the board using Trixx

I had a similar issue with a system with 4x 6950's.  It turned out to be heat related since the cards were so tight (i knew that was a bad idea!).  I opened it up and got a fan pointed at it and it stabilized quite a bit.  For the 6950's at least, when their temps get around 100c, it will drop the clockrate to cool the card.  MSI afterburner has some really good graphs you can watch to see what the system is doing (as well as overclock if you want)

is this a X-fire configuration ?

Most of what I've read suggests either disabling xfire or simply removing the xfire connection cable.  If you can't see some of the cards and are running windows, you may also need to buy or create a DVI:VGA "dummy plug" (although I udnerstand some new catalyst developments may remove this requirement)

There's no crossfire setup, temperature is stable at 82 degrees, dummy plugs are also plugged in.

same goes for me. I don't have crossfire. I'm not sure what dummy plugs are; but, the video cards are plugged straight to the mobo. Temperature-wise, GPU0 is about 5-10 C higher than GPU1 with the same overdrivectrl profile. So if anything GPU0 would have lower hash rate than GPU1?? But in my case, the GPU1 is lower than GPU0. Both are new cards purchased almost on the same date GPU0 arrived a week or so before GPU1.

DONT USE CROSSFIRE, it loses mhash, about 10 per card. Use extenders from your X1 PCI-E/PCI to x16 PCI-E. Use phatK kernel with ATI CARDS (5 and 6 series). I use 4 5850's and the first GPU as to be clocked down to 975 instead of 1000 for some reason as when all 4 cards are active, it starts to bomb the mhash above 975/300 clock. Very strange but think it might be a common thing maybe????

And GUI miner, Get rid. Pheonix seems to be the best for mhash but diablo is by far the easiest and if you install the 10.4 drivers (which include stream 2.1) then its not a lot to call between them. If you use phoenix, make sure all instacies run on 1 affinity (1 core) on your CPU as theres a bug that makes it 100% your cpu with 2 or more instances of it going. Causes the comp to run really slow, although the mhash doesnt seem to be affested ;)

O yes, VGA Dummy plugs make the cards that dont have a display connected, think it does, so it can be used by phoenix/diable ;)

http://www.geeks3d.com/20091230/vga-hack-how-to-make-a-vga-dummy-plug/