-Processor Revision Identifier (PRId) Register (15)

4.3 System Control Coprocessor

Processor Revision Identifier (PRId) Register (15)

The 32-bit, read-only Processor Revision Identifier (PRId) register contains information identifying the implementation and revision level of the CPU and CP0. Figure 4-15 shows the format of the PRId register; Table 4-11 describes the PRId register fields.

Figure 4-15 Processor Revision Identifier Register Format

Table 4-11 PRId Register Fields

The low-order byte (bits 7:0) of the PRId register is interpreted as a revision number, and the high-order byte (bits 15:8) is interpreted as an implementation number. The implementation number of the R4000 processor is 0x04. The content of the high-order halfword (bits 31:16) of the register are reserved.

The revision number is stored as a value in the form y.x, where y is a major revision number in bits 7:4 and x is a minor revision number in bits 3:0.

The revision number can distinguish some chip revisions, however there is no guarantee that changes to the chip will necessarily be reflected in the PRId register, or that changes to the revision number necessarily reflect real chip changes. For this reason, these values are not listed and software should not rely on the revision number in the PRId register to characterize the chip.

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