Thermal-Management Register 4 (Thrm4) - IBM PowerPC 750GX User Manual

User's Manual
IBM PowerPC 750GX and 750GL RISC Microprocessor

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.
0 1 2 3 4 5 6
Bits Field Name
0:23 Reserved
24:31 TOFFSET
Programming Model
Page 80 of 377
Reserved
7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
Reserved for future use. Always read as zeros.
Thermal calibration offset field set during factory test.
The °C offset value is in an 8-bit, signed, two's complement format.
TOFFSET
Description
gx_02.fm.(1.2)
March 27, 2006