Bitcoin Forum

Hello,

I just spent the last 8 hours trying to get cgminer running properly on a box running Xubuntu with two MSI Radeon 7950 cards running in it.

The issue is that I'm getting extremely low hashrates compared to running the card in windows with the same settings. Cgminer is reporting that one of the cards is heavily underclocked (300mhz core, 150mhz memory vs the expected 880mhz core and 1250mhz memory of a stock MSI 7950), and I'm unable to make core/memory speed changes to that card via cgminer (this card is cold to the touch with cgminer running). The other card responds to core/memory speed changes properly. Even the card that is clocked properly is giving pathetic hashrates vs what I see in windows with the same cgminer settings (~580 kH/sec at stock clock speeds).

Image:
https://i.imgur.com/J4rgu9X.jpg


Details:

- I followed the basic instructions here for installing Xubuntu, installing drivers and installing cgminer: http://tehgentoonoob.blogspot.com/2012/09/headless-mining-rig-with-xubuntu-1204.html (http://tehgentoonoob.blogspot.com/2012/09/headless-mining-rig-with-xubuntu-1204.html). Only real difference is I'm running Xubuntu 12.10 instead of 12.04, and using the latest version of cgminer (2.11.4). I didn't see any weirdness during setup, everything seemed to go as expected.

- Hardware consists of ASRock 970 Extreme4 mobo, AMD Sempron CPU, 8GB RAM, Seasonic 860w platinum PSU, and 2x MSI 7950 GPUs. Xubuntu is running off a 8GB Patriot USB stick.

- My cgminer startup script looks like this (parameters passed to cgminer are the same as what I use in Windows with much better results):

      #!/bin/sh   
      export DISPLAY=:0
      export GPU_MAX_ALLOC_PERCENT=100
      export GPU_USE_SYNC_OBJECTS=1
      cd /home/[myHomeDirectory]/cgminer-2.11.4-x86_64-built
      ./cgminer --scrypt -I 19 -g 1 -w 256 --thread-concurrency 21712 --auto-fan -o stratum+tcp://notroll.in:3333 -u [myusername] -p [mypassword] --failover-only -o stratum+tcp://coinotron.com:3334 -u [myusername] -p [mypassword]


I am not that experienced in linux, and would welcome any help/ideas that anyone has in troubleshooting.This is driving me crazy.

Thanks in advance!

And of course, I figure out the issue shortly after posting.

I needed to put a dummy plug into the 2nd GPU. I thought these were only necessary under Windows, but it turns out I was wrong.

If anyone else has an issue like this, you'll need to make one of these for each GPU that doesn't have a monitor connected:

http://www.overclock.net/t/384733/the-30-second-dummy-plug (http://www.overclock.net/t/384733/the-30-second-dummy-plug)

I'm now getting the expected hashrate on both cards.

Well, after watching the box for a little while, I actually seem to be getting about 10% less hashrate in linux than I do in windows (530 kH/sec in linux  per GPU vs 580 kH/sec in windows @ stock 7950 clock speeds).

Is that normal?