I did clean install of windows 10. And I have the same problem with long time required for windows to boot. After I have red somewhere online that might be a graphics driver causing the problem I deleted AMD drivers and boot time fell down from 1min 30sec to only 20 sec without amd driver. Just to mention that I tried many things and nothing worked, deleted all my programs, new chipset drivers, etc. I don't know which graphic card do you guys have, but it seems that we need to wait until they release update.
If your PC is still booting slow in a week or so then you may have issues that can be addressed.
For now, let Windows 10 do it's thing and 'doing that thing' will mean slow boot times for a while for some users.
And my pc has all the symptoms you mentioned, quick start till OEM screen and after that black screen for about 1:30s and then logon screen appears. Also HDD activity is strong during those 90 sec. Besides that, PC is working great and fast when it turns on.
Using Fast Startup of course has no issues when starting from off, but restarts adds the 30 seconds or so before login. I had read about issues with AMD and reverting back to an older Catalyst fixing the black screen before login, but I have NVidia and used DDU and did a couple restarts with no change... still 30 seconds of black screen before login with heavy HDD activity. <shrug>
Just an update, I have done yet another clean install. This time I installed all programs I wanted - EXCEPT for the Intel Rapid Storage, and Comodo Firewall.
It boots a bit faster, the black screen no more than 40 seconds (as compared to 1:20 before).
For my computer, if I do not install Intel HD Graphics, I can not even put the PC to sleep or dim the screen. So it probably is not an option for me.
I recently had a boot delay problem on a Windows 8.1 system which was caused by a partition on an active USB HDD being set to active. Check the partition status and ensure only your main boot drive is set active and other discs inactive. I used Mini Tool Partition Wizard to do this.
I found another solution.
"1) Download the install AMD Radeon Windows 10 drivers that were released couple of days ago. 15.7.1 I believe.
2) After installing rebooting, go to regedit. In regedit, go to the Find option in the Edit Menu.
3) Search for EnableULPS. Double click on it and change the value from 1 to 0.
4) Exit regedit and restart your laptop.
5) Your boot and sleep times should be much, much better."
Some antivirus programs can slow things down as well. Not having the correct drivers is usually the main cause, and if they haven't provided the drivers, that tells me they probably don't have a very recent BIOS update (which is also problematic for start times).
The best drivers for your system are Win 10 from the device manufacturer. Intel states this themselves, though they still provide drivers for those who have problems getting it from the manufacturer. So many people are complaining about Win 10 not working, only to discover that they don't even have the 'right' drivers installed. Granted MS offered them the chance to upgrade in the first place, they didn't search for the right drivers beforehand.
Other than that, you might be able to speed things up a bit with this tutorial from the eightforums: Optimize Performance of Windows 8