• Fundamentals of operating systems
• OS/2 Architecture - A Programmer's Overview (Scott E. Garfinkle, 2000, OpenOffice.org format)
• RUS: Internal structure of OS/2 Warp
• IBM Redbooks

• SG24-4630-00 OS/2 Warp (PowerPC Edition) A First Look
• SG24-4639-00 OS/2 Warp (PowerPC Edition) Graphical Subsystem

In OS/2 and eCS systems, all the platform specific code from the operating system is removed and placed into platform specific drivers. These drivers provide an abstraction layer for the underlying hardware by allowing the OS to call generic functions to perform platform specific operations without worrying about the actual hardware implementation. The objective of the PSD drivers is to allow for the support of new hardware platforms without modifying the operating system.

There are two PSD drivers:

• OS2APIC.PSD (old, IBM)
• ACPI.PSD (current version)

Notes: The PSD mechanism was implemented not perfect.