I have the same cards with the same problem. On slot 1 pci-e 3.0 card runs 12 degrees hotter than the other on pci-e 2.0. Voltage is locked unfortunately. I hope we find a solution soon.
is there any method to unlock voltage?
i have done that with trixx for sapphire. Maybe it will work with your card. My card is Sapphire Vapor-X R9 280x
I need some help with the config. I only get about 560 kh
here my config
cgminer -o stratum+tcp://coinotron.com:3334 -u ** -p ** --scrypt -I 20 -g 2 -w 256 --thread-concurrency 8192
1038 GPU
1500 Mem.
Big Thanks