From Beyond BIOS: Implementing the Unified Extensible Firmware Interface with Intel's Framework

CSM: A Bridge between Innovation and Tradition

The computer industry usually experiences a transition period between the introduction and adoption of a new technology. The Framework also expects a natural transition phase, brief or prolonged. The CSM eases this transition phase by acting as a bridge between EFI and legacy BIOS interfaces. The CSM allows EFI to use legacy BIOS interfaces to boot to a traditional operating system such as DOS, Windows 2000, Windows XP, and so on. The CSM also allows EFI to boot to an EFI-aware operating system from a device controlled by a traditional Option ROM. With the advent of CSM, a system vendor can participate seamlessly in the innovation of new technology EFI without sacrificing any of its traditional functionalities. Therefore, directly and indirectly, CSM plays a vital role in ensuring the existing functionality while the industry pursues the transition from legacy BIOS to EFI.

The CSM uses the Framework for platform and hardware initialization, enumeration, and boot path selected by EFI. Additionally, the CSM provides the EfiCompatibility functionality to EFI in supporting traditional operating systems and traditional Option ROMs. The EfiCompatibility module along with the IBV supplied Compatibility16BIOS and Compatibility16SMM modules constitute the CSM. During the transition from legacy BIOS to EFI, the traditional Option ROM support may be required longer than traditional operating system support. The CSM is modular and hence can be removed if not required. Figure 17.1 represents a block diagram of how a legacy system operates using the CSM under the...


Products & Services
NVRAM
NVRAM memory chips (Non-volatile RAM) is used to store configuration information that can be changed through modem commands. 
Computer-on-Module (COM)
Computer-on-Modules (COM) are highly integrated single-board computers built on a single circuit board. They are used in embedded applications.
Ruggedized Computers
Ruggedized computers are similar to personal computers (PC), but they are intended for use on a factory floor or in other harsh environments.
Pulsation Dampeners
Pulsation dampeners are devices that control the pulsations that result from a pressurized system's stroking action. They are often referred to as accumulators or surge suppressors.
Analog Modem-to-Cellular Converters
Analog modem-to-cellular converters allow legacy equipment with built-in analog modems to connect to the cellular data networks by emulating the traditional dial-up PSTN network.

Topics of Interest

CSM Architecture The CSM empowers EFI with the ability of loading a traditional operating system and using a traditional Option ROM. The CSM consists of five main components: EfiCompatibility...

Functional Visualization of CSM After all necessary DXE drivers are executed and the DXE Foundation produces the EFI Boot Services and EFI Runtime Services, the DXE Dispatcher transfers the control...

EfiCompatibility (CSM32) EfiCompatibility consists of the Legacy BIOS Driver with various protocols: Legacy BIOS Protocol Legacy BIOS Platform Protocol Legacy Region Protocol Legacy 8259 Protocol...

Come visit me, here in this better street. Pretend you are a white rabbit Harlan Ellison Overview The average user is unaware of how much goes on behind the scenes in the operation of a modern...

Compatibility16BIOS (CSM16) The Compatibility16BIOS module can be thought of as the runtime image of the legacy BIOS without the POST and Setup. The design goal is to make the Compatibility16BIOS...