I am running this board with 8GB RAM and Win10 Pro x64 and according to Asrock for Win10 users the firmware upgrade preference is to use Instant Flash or Internet Flash in the UEFI setup.
I tried both options and always failed with a popup box stating "Secure Flash Check Fail" message.
Together with asrock support I tried several options to get either Instant Flash or Internet Flash to work.
Both to no avail. Internet flash did not detect internet and always asked to check my internet settings
and instant flash always complained "Secure Flash check Fail"
Solution: all done within Win10
I went to the AMI Megatrends Website to get:
unpacked the file and went to
\AMI\AMIBIOS_and_Aptio_AMI_Firmware_Update_Utility\amiflash\Aptio\afuwin\64\afuwin64\AfuWin64 and started AFUWINGUI.EXE
Flashed Asrock Bios from 1.20 to 1.50 using AMI Megatrends Aptio AFUWINGUI V.3.07.01 x64 with the following setup:
Tick the following boxes:
Program all Blocks
Main BIOS Image
Do not Check ROM ID
Bios 1.50 downloaded from Asrock site and renamed to Q1900TM150.ROM
After completion, shutdown PC
At next boot goto F2 Bios setup, F9 Load UEFI defaults, F10 Save and reboot again.
After that, get into updated BIOS using F2 and adjust to your liking.
Hope it helps