4.3.6. c0, Multiprocessor Affinity Register

The MPIDR characteristics are:


Enables CPUs to be recognized and characterized within a twin-CPU system.

Usage constraints

The MPIDR is:

  • a read-only register

  • accessible in Privileged mode only.


Available in all processor configurations.


Figure 4.11 shows the MPIDR bit assignments.

Figure 4.11. MPIDR bit assignments

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Table 4.7 shows the MPIDR bit assignments.

Table 4.7. MPIDR bit assignments


Multiprocessing extensions:

0b00 = no multiprocessing extensions, applies to Cortex-R5, r0p0

0b11 = processor is part of a uniprocessor system, applies to Cortex-R5, from r1p0.

[15:8]Aff1Processor groups within a system. Read GROUPID input.

Processors within a group:

0x0 = CPU0

0x1 = CPU1, if implemented.

To access the MPIDR, read CP15 with:

MRC p15, 0, <Rt>, c0, c0, 5 ; Read MPIDR
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