HD7950 multi-GPU issues
Hi all, I have been having some problems getting 2x7950's working with oclHashcat using Debian Wheezy. I have installed a stock Debian wheezy with OpenCL headers and the "amd-catalyst-14-4-rev2-linux-x86-x86-64-may6.zip" drivers, this shows two GPU's present with amdconfig and I used aticonfig to set both cards for use with X11. The devices appear to function fine, when I run oclHashcat (without any AMD SDK installed) it can see only ONE GPU card and will benchmark and crack hashes on a single 7950 just fine. I added the AMD SDK "AMD-APP-SDK-v2.9-lnx64.tgz" to the host (as I also wish to use John the Ripper with GPU support) and then when I run oclHashcat, two devices are detected but complains the incorrect or non-official drivers are installed, when I use --force I receive the error "clBuildError() -11" (or similar, I forget the exact API call as the box is nuked again). I read that perhaps this could be due to the versions of driver installed and so have tried (without success) to rotate the drivers to alternative versions and with AMD SDK 2.7 through to 2.9, all giving similar results or breaking the box horrifically (requiring a rebuild.)

Has anyone any tips for the precise software driver version I should be using or why I am experiencing this error? Both GPU's seem fine under amdconfig and I can use a single GPU pre-AMD SDK install but I could really use both functioning as I have a pile of hashes I would like to crack.

Kind Regards,
Hacker Fantastic
This wiki entry is updated and tells you what you need to do. The drivers can be weird, so if it's still not working, make sure you follow this exactly. For example, the wiki entry says to use Ubuntu Server. Debian Wheezy may or may not work right (even though they're all Debian based, there are slightly different kernel versions and who knows what other differences).