TABLE OF CONTENTS I just invent, then wait until man comes around to needing what I invented.
R. Buckminster Fuller
EFI has over time evolved a very basic paradigm for establishing a firmware policy engine. The concept was developed prior to the inception of the framework (EFI 1.1 or earlier) of a single boot manager whose sole purpose was exercising the policy established by some architecturally defined global NVRAM variables. As the framework evolved, and several distinct boot phases such as SEC, PEI, DXE, BDS, Runtime, and Afterlife were defined, the BDS (Boot Device Selection) phase became a distinct Boot Manager-like phase. In this chapter, the architectural components that steer the policy of the Boot Manager are reviewed. This content forms the architectural basis for what eventually became the BDS phase. Selection
In fact, the differences between what is known as the boot manager in pre-Framework solutions and what is known as the BDS in Framework solutions is easy to illustrate. Figure 13.1 shows the software flow in an EFI 1.1 compatible (pre-Framework) environment, and Figure 13.2 shows one that is Framework compatible.
As you can see from comparing the two figures, there is much overlap. The BDS phase subsumes the direction described in this chapter and is further explained in Chapter 9.
The EFI boot manager is a firmware policy engine that can be configured by modifying architecturally defined global NVRAM variables. The boot manager attempts to...
