Data Sheet
PowerPC 970FX
Preliminary
Figure 5-3. PowerPC 970FX Thermal Diode Implementation
Thermal Diode Implementation
Low Temp TD Reading
12 bits
Two voltages and two temperatures
stored in fuse string
12 bits
Elevated Temp TD Reading
Low Temp = -40C + 1C*fuse string
Note: this does not imply
(range: -40 to 88C)
an operating temperature
Low Temperature
7 bits
Elevated Temperature 7 bits
Elevated Temp = 1C*fuse string
(range: 0 to 128C)
Voltage (mV) = (fuse string/2) + 300
Voltage
(range = 300 to 2348mV)
mV low
After correlation between mV readings at
User (part ON) vs IBM (part OFF). User
can use IBM’s slope and intercept to
determine Set Point.
mV elev
User's (mV)
Set Point
Temp
Low
Temp
Elevated
Temp
User's
Max Temp
Table 5-9. Thermal Diode Data Encoding
Offset within
First 64-Bit Read
Field Name
Ring Position
Length in Bits
Adjustment
temp_low
temp_high
1546:1552
1553:1559
1560:1571
1572:1583
39:46
7
7
Value - 40
None
32:38
voltage_low
voltage_high
20:31
12
12
Value/2 + 300
Value/2 + 300
8:19
Note: All values are stored LSB:MSB (bit reversed). They should be bit-swapped before applying
the adjustments shown in this table. Temperatures are stored in degrees Centigrade and voltages
are stored in millivolts.
System Design Information
Page 70 of 74
October 14, 2005
IBM [ IBM ]
