Extensible Firmware Interface Specification v1.10
The UGA Protocol sections of this specification were developed in close consultation with Microsoft as part of the Universal Graphics Adapter (UGA) initiative. Microsoft has made significant contributions to the interface definitions presented here to ensure that they will work well with video adapters supporting the Microsoft UGA ...specification. These efforts are gratefully acknowledged. The EFI Byte Code Virtual Machine sections (Chapter 19) of this specification were developed in close consultation with Microsoft, LSI, Hewlett Packard, Compaq, and Phoenix Technologies. The efforts of all contributors to these sections are gratefully acknowledged.
This Extensible Firmware Interface (hereafter known as EFI)Specification describes an interface between the operating system (OS) and the platform firmware. The interface is in the form of data tables that contain platform-related information, and boot and runtime service calls that are available to the OS loader and the OS. Together, these provide a standard environment for booting an OS.
The EFI specification is designed as a pure interface specification. As such, the specification defines the set of interfaces and structures that platform firmware must implement. Similarly, the specification defines the set of interfaces and structures that the OS may use in booting. How either the firmware developer chooses to implement the required elements or the OS developer chooses to make use of those interfaces and structures is an implementation decision left for the developer.
The intent of this specification is to define a way for the OS and platform firmware to communicate only information necessary to support the OS boot process. This is accomplished through a formal and complete abstract specification of the software-visible interface presented to the OS by the platform and firmware.
Read the full Extensible Firmware Interface Specification.