User’s Manual
IBM PowerPC 750GX and 750GL RISC Microprocessor
Programming Model
Page 80 of 377
gx_02.fm.(1.2)
March 27, 2006
2.1.4.3 Thermal-Management Register 4 (THRM4)
Due to process and thermal sensor variations, a temperature offset is provided that can be read via an mfspr
instruction to THRM4. The TOFFSET field is an 8-bit signed integer that represents the temperature offset
measured; it is burned into the THRM4 Register at the factory to allow for enhanced accuracy. When in TAU
single-threshold or dual-threshold mode, TOFFSET should be subtracted from the desired temperature
before setting the THRMn(THRESHOLD) field. In junction-temperature-determination mode, TOFFSET must
be added to the final threshold number to determine the temperature. The temperature, in °C, equals:
THRMn[THRESHOLD] + sign-extended [TOFFSET]
The THRM4 register can be accessed with the mfspr instruction using SPR 920.
Reserved TOFFSET
012345678910111213141516171819202122232425262728293031
Bits Field Name Description
0:23 Reserved Reserved for future use. Always read as zeros.
24:31 TOFFSET
Thermal calibration offset field set during factory test.
The °C offset value is in an 8-bit, signed, two’s complement format.
