MSDN has published Kernel Enhancements for Windows XP:
Microsoft has made many enhancements to the kernel of the next release of the Microsoft® Windows® operating system, Windows XP. This section provides an overview of the new features and changes in the kernel for Windows XP, intended for system and peripheral designers, driver developers, and firmware developers who are creating products that run on Windows XP.
This documentation assumes that the reader is familiar with related concepts and issues for Windows 2000. For more information, see the Windows Driver Development Kit and the Windows 2000 Resource Kit (available through MSDN® Professional subscription or through Microsoft Press®).
Kernel improvements are significant because the kernel provides low-level operating system functions, including thread scheduling, interrupt and exception dispatching, multiprocessor synchronization, and a set of routines and basic objects used by the rest of the operating system to implement higher-level constructs.
This documentation describes the kernel improvements for Windows XP, which include:
Larger registries, limited only by available system disk space. Improved algorithms for faster queries.
Cross-session debugging, new quit and detach command for debugging without killing the application, and built-in user mode heap-leak detection.
New input/output (I/O) interfaces for performance enhancement, while retaining compatibility with Windows 2000 drivers. Kernel-mode support routines for File System Filter driver improvements. Support for performance measurements in retail code, and improved low-memory performance.
Broad range of improvements, including logical prefetch to improve boot and logon performance, reduced paged pool usage, enhanced terminal server support, support of giant drivers, and Windows XP execution from ROM.
Native support for processor performance control, including Intel SpeedStep Technology, AMD PowerNow!, and Transmeta LongRun for longer mobile computer battery life. Hibernate, standby, and resume performance have been greatly improved.
Improved Boot and Logon Performance
When a Windows XP system is first booted, data is saved about all logical disk read operations. On later boots, this information is used to pre-fetch these files in parallel with other boot operations.
For "lights-out" datacenter deployment and remote administration.
Provides better performance for Cache Coherent–Non Uniform Memory Architecture (ccNUMA) computers, as well as an interface to let applications tailor their execution characteristics in the ccNUMA environment.
The Windows XP kernel improvements provide new opportunities for independent software vendors (ISV), independent hardware vendors (IHV), and other value-added providers working with Windows 2000. Windows XP provides compatibility with Windows 2000 devices and drivers, while providing new routines, enhancements, and other features that can be leveraged into future products and services.