Topic: RX470-Win10-XMR-Stak-AMD: Selected OpenCL device index 4 doesn't exist (SOLVED) (Read 191 times)

I'm posting this one to help other people in troubleshooting rigs with RX470, Windows 10 and XMR-Stak-AMD.
My rig was working OK (sometimes frozen but nothing to worry about after a restart of the rig). Yesterday after a restart, I got a bit upset because the rig was not working at all with the RX470 cards. When I was starting the XMT-Stak I was getting the following message:

[2018-01-30 12:41:37] : WARNING: backend NVIDIA disabled.
[2018-01-30 12:41:38] : Compiling code and initializing GPUs. This will take a while...
[2018-01-30 12:41:39] : Selected OpenCL device index 4 doesn't exist.

[2018-01-30 12:41:39] : WARNING: AMD device not found
[2018-01-30 12:41:39] : WARNING: backend AMD disabled.
[2018-01-30 12:41:39] : Starting 1x thread, affinity: 0
....

Long story short, for some reason the mining software did not recognise the 5th card (index 4). This was validated by deleting the amd config file at letting XMR-Stak to rebuild it; at that point it stopped to index 3 and then moved on to start mining over the pool.
Tried different things I have read in the net like changing the Platform manually form 1 to 0 but nothing worked. AMD tools were showing that the card was alive and working OK - so no issues from there.

What fixed the issue with XMR-Stak was to enter to system BIOS (not GPU) and save the card configuration (just change the card has the issue and set it back so it will allow you to save the BIOS again). Then I run the XMR-Stak with the 6 card configuration file and everything work perfectly.