OOK.. I got it.. What a nightmare. Just to let you know. From Version 13.12 on AMD has changed some entrys in their driver, related to the registry.
The result of this change is in some Asrock H81 BTC Pro R2.0 and Asrock H81 BTC Pro, it is not possible run more then 4, or 5 GPUs.
There is a verry good, working fix available.
Here is a good tutorial and all you need to fix it.
https://lbr.id.lv/coin/6xgpu/13-12_mod-v3_README.htmlRegards,
Scandalrosi