If you're running Windows 10 on a laptop with an AMD Radeon graphics chip, with intel switchable graphics (for low-power or 2D mode), you may be experiencing a terribly frustrating black screen before login and between applications.  This black screen could last for minutes before you regain control of your computer.  I feel your pain!

The short story is AMD has deemed your laptop too old.  Yes it may only be a couple years, but the only OFFICIAL way to fix this problem is to buy a new laptop.  Gee thanks.  In reality, they messed up the driver and refuse to fix it.  Apparently if you install an older version of the Catalyst driver (15.7?) the problem goes away.  At least until Windows auto-updates your driver for you.

Some folks claim to have success by forcing switchable graphics in Catalyst Control Center to maximum performance or maximum power-saving, to minimize "switching".

Since the problem is the newer AMD driver does not properly support ULPS (Ultra-Low Power Savings) on "legacy" chips, turning that feature off in the registry worked for me.  Here's where I found that solution: http://www.tomshardware.com/faq/id-1904869/disable-ulps-amd-crossfire-setups.html

Quoted Text

Step 1
Go to the registry by typing "regedit" in windows search.

Step 2
Go to the "Edit" tab and click on "Find".

Step 3
In the text box type in "EnableULPS" and then press Find.

Step 4
You should see "EnableULPS". Double click on it.

Step 5
Change the value from "1" to "0"


Recap
ULPS should now be disabled. Although you can opt to disable it in Afterburner and Catalyst Control Center, it often gets turned back on after an update and so doing this is more efficient.

Note: If you want to turn ULPS back on, simply change the value back to "1".

For good measure, I rebooted after making that change and found the black screen problem had disappeared!  Hurray!