Chapter 3 - OSF/1 Memory Management (III)

Abstract

This chapter discusses OSF/1 Memory Management. Memory management provides the mechanism to map the active part of the virtual address space to the available physical address space. The operating system controls the virtual-to-physical address mapping tables and saves the inactive (but used) parts of the virtual address space on external storage media. Physical addresses are at most vaSize-2 bits. This allows all of physical memory to be accessed via kseg. A processor may choose to implement a smaller physical address space by not implementing some number of high order bits. The two most significant implemented physical address bits select a caching policy or implementation dependent type of address space. Implementations will use these bits as appropriate for their systems. Memory management is always enabled. Implementations must provide an environment for PALcode to service exceptions and to initialize and boot the processor, for example, PALcode might run with I-stream mapping disabled.