if your system has a battery with no charge the BIOS should report setting required and give you the choice to enter during
boot-up. This also happens when you have removed the battery and have no replacement soldered on or on external hook-up.

However the system does not have a normal BIOS button prompt during boot-up and thus is not able to be accessed during boot.
This can be annoying if you have no floppy drive or a corretly configured hard drive installed.


The easyiest option is to boot-up to DOS prompt from either floppy disk or local hard drive and then press  Ctrl+Alt - S. 
This will load the BIOS setup program and then with any changes re-boot the machine.
This is the correct way to enter the BIOS on Amstrad PC7386SX Mainboard.