-Virtual Address Space

4.2 Address Spaces

Virtual Address Space

The processor virtual address can be either 32 or 64 bits wide,*1 depending on whether the processor is operating in 32-bit or 64-bit mode.

In 32-bit mode, addresses are 32 bits wide. The maximum user process size is 2 gigabytes (231).
In 64-bit mode, addresses are 64 bits wide. The maximum user process size is 1 terabyte (240).

Figure 4-1 shows the translation of a virtual address into a physical address.

Figure 4-1 Overview of a Virtual-to-Physical Address Translation

As shown in Figures 4-2 and 4-3, the virtual address is extended with an 8-bit address space identifier (ASID), which reduces the frequency of TLB flushing when switching contexts. This 8-bit ASID is in the CP0 EntryHi register, described later in this chapter. The Global bit (G) is in the EntryLo0 and EntryLo1 registers, described later in this chapter.

Copyright 1996, MIPS Technologies, Inc. -- 21 MAR 96

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