Os/Pxe Boot - HP ZBook 15 G2 Technical White Paper

Technical white paper | HP ZBook 15 G2 Mobile Workstation

OS/PXE Boot

HP ZBook 15 G2 Mobile Workstation users may encounter difficulties loading a
Windows 7 image onto a system that is pre-loaded with Windows 8. This
problem stems from a system conflict in the preboot execution environment
(PXE, often pronounced 'pixie'): Windows 7 does not support Secure Boot, a
UEFI BIOS feature enabled in Windows 8 systems. When Windows 7 is loaded
on a Windows 8 system, the Secure Boot firmware blocks the launch of the OS.
Secure Boot overview
Secure Boot is a feature to ensure that only authenticated code can start on a platform. The firmware is responsible
for preventing launch of an untrusted OS by verifying the publisher of the OS loader based on policy, and is designed to
mitigate root kit attacks.
Figure 1. UEFI Secure Boot flow
• Firmware enforces policy and only starts signed OS loaders it trusts.
• OS loader enforces signature verification of later OS components.
• The UEFI BIOS checks the signature of the OS loader before loading. If the signature is not valid, the UEFI BIOS will stop
the platform boot.
BIOS and UEFI background
As computer technology has advanced, the BIOS has expanded to handle new components, larger and more complex
chipsets, add-in cards, and other enhancements. This expansion has made the BIOS increasingly intricate. Development
of the Unified Extensible Firmware Interface (UEFI) is the computer industry's solution to BIOS limitations. UEFI is a set of
modular interfaces that replaces the set of traditional BIOS interfaces between the OS and platform firmware.
UEFI is derived from high-level C language and is driver-based, scalable, and easy to debug and upgrade. UEFI uses a
modular, platform-independent architecture that can perform boot and other BIOS functions. For more information
about UEFI, go to hp.com/go/techcenter.
2
Native
UEFI
Verified OS
loader
(e.g. Win8)
OS start