I have previously mined on a Sapphire Radeon Nitro R7 370: the hash rate was roughly 13Mh/s.
I decided to upgrade and bought a Sapphire Radeon Nitro R9 390. Knowing of a bottleneck, I have overclocked the first GPU to parameters of the second (which is the primary video card).
First of all, I find it surprising that the total hash rate is barely 33Mh/s.
Secondly, when I run ethminer, both GPU's work at 100% but there are barely any solutions being found (I'm mining in a pool). The power unit is large enough to accommodate both GPU's, I've tried removing the old GPU but it did not help at all. Reinstalled windows but still no luck. I've also overclocked the PCI-e speed to 150Mhz. No luck. I do understand that its not a pool issue, but rather hardware related.
Latest drivers installed, tested the videocards by playing different games, but it worked fine. Any suggestions to possible solutions?