Problem description.
===============
1. Blender MultiGPU Render not working for me with Adrenalin 17.12.2 on Windows 10 64bit.
2. Uninstall Adrenalin 17.12.2, reboot.
3. Reinstall 17.4.4 WHQL
4. Run Blender 2.78c and 2.79 on BMW_gpu Demo testcase. Both run as expected. MultiGPU works. In 2.78c Rendering runs on 3 R9 Nanos and 1 R9 280x. In 2.79 rendering runs on 3 R9 Nanos.
5. Uninstall 17.4.4 WHQL, reboot.
6. Reinstall Adrenalin 17.12.2, reboot.
7. Run Blender 2.78c and 2.79 on BMW_gpu Demo testcase. MultiGPU not working as expected. In 2.78c Rendering runs on 1 R9 Nano and 1 R9 280x. In 2.79 rendering runs on 1 R9 Nano.
In all cases Crossfire is turned off.
I tested 17.4.4 WHQL because that is the Driver Version I am stuck on for Windows 8.1 64bit OS since AMD dropped support for Windows 8.1 64bit OS.
I normally use Windows 8.1 64bit OS with WHQL 17.4.4 for Blender work. Both Blender 2.78c and 2.79 MultiGPU works fine on that OS and with that AMD Driver.
System Information.
Motherboard Asus Z97 Deluxe.
CPU i7-4790K.
GPU Tripe R9 Nanos connected over PCIe3.0x8, PCIe3.0x8, PCIe2.0x4 and a single R09 280x connected via PCIe2.0x1.
OS / Drivers tested Windows 8.1 64bit with Crimson ReLive WHQL17.4.4 (works) and Windows 10 64bit with Adrenalin 17.12.2 (Fails) and Crimson ReLive WHQL17.4.4 (works).
R9 280x GPU is connected to motherboard using PCIe2.0 to USB3.0 to PCIe_16 GPU Mining Adapter.
I believe AMD did lots of work with the Blender Team to improve AMD Feature set and performance in Blender 2.79, versus 2.78c. It is a pity to see this not working with the Adrenalin 17.12.2 Driver.
Also unfortunately GCN 1.0 card support is not available in Blender 2.79, I believe this is because of a fix needed in the OpenCL Driver for GCN1.0 cards. It would be good to see something done on that issue. In my case I loose one card (R9 280x) when rendering in Blender 2.79. So for me, Rendering the BMW_gpu benchmark on 2.79 is slower with 3 R9 Nanos than rendering on Blender 2.78c with 3 R9 Nanos and 1 R9 280x.
I will file another AMD Reporting form.
If anyone else has noticed this issue with Blender MultiGPU on Adrenalin Driver please let me know.
Meantime I will go back to running Blender 2.78c/2.79 on Windows 8.1 64bit OS with the working WHQL 17.4.4 driver.
