Hi,
I have exactly the same issue and have investigated extensively to find a solution. I have 2 miners with the following set-up;
1/ AsRock H81 Pro BTC (BIOS version 1.5) with 5x Sapphire R9 280X Toxic running on Windows 8.1
- AMD Catalyst driver 14.6 installed
- sgminer 4.?.? MODB2 (will try newer versions later on, but it works fine)
- using flat ribbon non-powered risers
- 4.3 MH/s per GPU and runs stable 24/7
2/ AsRock H81 Pro BTC (BIOS version 1.5) with 5x Sapphire R9 290X Tri-X running on Windows 8.1 with
- AMD Catalyst driver 13.12 installed, but with the applicable AMD driver 14.6 opencl files in the sgminer directory
- currently sgminer 4.?.? x11x13mod (have tried almost all of them)
- currently using USB powered risers, but have also tried with flat ribbon non-powered risers
- 5.0 MH/s per GPU, but have not found the best sgminer configuration settings (speed should be near 6 MH/s per 290X card)
- have been trying to find a 24/7 stable configuration for weeks
The Windows OS of both miners indicate a Code 43 error in System\Device Manager when I add a 6th GPU to the motherboard.
None of the custom/modified drivers or work-arounds provided at litecointalk.org worked for me. I tried them all, following the instructions to the letter.
Any help would be appreciated.
PS: I still have to try if it works with Ubuntu (still on todo list).