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3.2.6. c0, Multiprocessor ID Register

The Multiprocessor ID Register indicates that the processor is a uniprocessor.

The Multiprocessor ID Register is:

  • a read-only register that is Read-As-Zero

  • accessible in privileged modes only.

Table 3.11 shows the results of attempted access for each mode.

Table 3.11. Results of access to the Multiprocessor ID Register[5]
Secure privilegedNonsecure privilegedSecure UserNonsecure User
ReadWriteReadWriteReadWriteReadWrite
DataUndefinedDataUndefinedUndefinedUndefinedUndefinedUndefined

[5] An entry of Undefined in the table means that the access gives an Undefined Instruction exception when the coprocessor instruction is executed.


To access the Multiprocessor ID Register, read CP15 with:

MRC p15, 0, <Rd>, c0, c0, 5; Read Multiprocessor ID Register