Boot process with boot manager in primary partition
There are two possibilities:
Boot manager partition is permanent active
This possibility is present in all previous versions of Boot-US.
Initially the boot process is identical
to the standard boot process.
Thus the BIOS loads the MBR which
searches for an active partition and loads the corresponding boot sector.
The active primary partition on the first hard disk is that partition in which
the boot manager of Boot-US is installed. This partition must be permanetly active. The first sector
of this partition contains the first part (LOADR-US) of the boot manager.
The task of LOADR-US is --- similar to a boot sector --- to load the
main part (BMGR-US) of the boot manager and start it.
BMGR-US shows a menu with all configured partitions and waits for the
user to select a particular partition. Then BMGR-US loads the boot sector
of the selected partition from one of the local hard disks or from the
diskette and executes the code found on the boot sector. In this way the
selected partition is finally booted.
Boot manager partition is not active
This possibility is implemented the first time with Boot-US 3.0.0.
Technically the boot process is similar to the boot process with boot manager in MBR.
The BIOS loads the MBR which contains now the first part of the boot manager (LOADR-US).
This code from the MBR loads directly the first sector of the boot manager partition, which in turn loads the complete boot manager.
The contents of the boot manager partition is identical in both cases. Only the code in the MBR is different.
In the second case it does not search for the active partition instead it directly loads the boot manager partition.