Core 2 Duo Temperature Guide Updated April 21st, 2007
Scope
The purpose of this Guide is to provide users with an understanding of thermal relationships, so that C2D platforms can be uniformly tested, properly analyzed, and accurately monitored. This Guide is not an Engineering Document, and does not address unnecessarily diverse or complex technical details. Certain strict definitions have therefore been relaxed to simplify concepts and enhance comprehension. This Guide applies to air cooled mainstream Desktop C2D processors.
Background
Intel has 2 distinct C2D thermal specifications, and provides a test program, Thermal Analysis Tool
(TAT), to simulate 100% Load. Some users may not be aware that
Prime95, Orthos, Everest and assorted others, may simulate loads which are intermittent, or less than TAT. These are ideal for stress testing CPU, memory and system stability over time, but aren't designed for testing the limits of CPU cooling efficiency.
Some users also may not know that C2D's feature 3 sensors at 2 different temperatures; a
single on-die Tcase sensor (between the Cores), and
dual Tjunction sensors (one within each Core). Consequently, there is much confusion regarding specifications, calibration Offsets and test methods, so results can be difficult to decipher and compare. Therefore, when expressing Idle & Load test Results, it's also necessary to define the Variables as:
Results
Tcase = Idle & Load
Tjunction = Idle & Load, Hottest Core
Variables
Ambient = Intake Temp
Chipset = Model
C2D = Model
CPU Cooler = Model
Frequency = CPU Clock
Load = Test Program
Motherboard = Model
Vcore = CPU Voltage
Specifications
Intel's Thermal Specification:
http://processorfinder.intel.com/details.aspx?sSpec=SL9S8
Thermal Specification:
*
The thermal specification shown is the maximum case temperature at the maximum Thermal Design Power (TDP) value for that processor. It is measured at the geometric center on the topside of the processor integrated heat spreader.
X6800 = ~ 60c, Vcore max = 1.3525, TDP = 75w
E6XX0 = ~ 60c, Vcore max = 1.3525, TDP = 65w
E4XX0 = ~ 60c, Vcore max = 1.3250, TDP = 65w
** For processors without integrated heat spreaders such as mobile processors, the thermal specification is referred to as the junction temperature (Tj). The maximum junction temperature is defined by an activation of the processor Intel® Thermal Monitor. The Intel Thermal Monitor?s automatic mode is used to indicate that the maximum TJ has been reached.
Ambient Temperature = 22c
Idle to Load Delta Max = 25c
Tcase to Tjunction Delta = 15c
Thermal Sensor Accuracy = +/-1c
Interpretation
* The first part of the spec refers to a single measuring point on the integrated heat spreader, which is in contact with the CPU cooler. Since there is no laboratory test sensor at this location,
the CPU Case Thermal Diode is used to display the CPU temp in BIOS, where thermal tables are stored to emulate the heat spreader. This is the CPU die temperature measured between the Cores. Thermal Case Temperatures of 60c is hot, 55c is warm, and 50c is safe. The single CPU Thermal Case sensor is how Tcase is measured, and is the CPU temperature displayed in BIOS, Motherboard Utilities, and SpeedFan: CPU or Temp X.
** The second part of the spec refers to mobile processors without an integrated heat spreader, measured by internal Digital Thermal Sensors. Since Intel's Thermal Analysis Tool (TAT) is a Notebook tool, and desktop C2D's have an integrated heat spreader, TAT will typically indicate ~ 2c lower than SpeedFan. These are the dual Core temperatures measured within the hot spot of each Core. Thermal Junction temperatures of 75c is hot, 70c is warm, and 65c is safe. The dual Thermal Junction sensors are how Tjunction is measured, and are the dual Core temperatures displayed in TAT, and SpeedFan: Core 0 / Core 1.
Thermal Flow
Heat originates within the Cores, and is hottest where the dual Tjunction sensors are located. Heat is then dissipated throughout the CPU die to the socket and motherboard, and to the Integrated Heat Spreader, where the single
Tcase sensor is located between the Cores, and the temperature is ~ 15c cooler. Heat is then transferred to the CPU cooler, and finally to air inside the computer case. All 3 C2D temperatures are then determined by computer case cooling efficiency and Ambient temperature.
Regardless of Load, Tjunction is always ~ 15c higher than Tcase, and Tcase is always higher than Ambient.
Findings
(A)
TAT can be used simultaneously with SpeedFan for benchmarking Desktop C2D's at 100% Load.
(B) The Delta between Tcase (BIOS, Motherboard Utilities and SpeedFan: CPU or Temp X) and Tjunction (TAT and SpeedFan: Core 0 / Core 1) is ~ 15c +/- 3c.
(C)
50c Tcase and 65c Tjunction are safe and sustainable temperatures.
Overclocking
Intel's Thermal Design Power (TDP) spec of 65 watts can be exceeded by over 50% when CPU frequency is aggresively overclocked, and Vcore is increased to maintain stability. Intel's Vcore max spec of 1.3525, when increased much beyond 10%, or 1.5 Vcore, makes it challenging to maintain safe temperatures with air cooling. As Ambient temperature increases, overclock frequency and Vcore may need to be decreased.
Every CPU is unique in it's overclock potential, voltage tolerance, and thermal behavior. If the maximum stable overclock is known at 1.35 Vcore, then each increase of .05 volts will typically allow a stable increase of ~ 100 Mhz, and will result in a corresponding increase in CPU temperatures of ~ 3 to 4c. Vcore is the most predominant Variable affecting temperatures.
At 1.35 Vcore, ~ 300 Mhz of additional overclock remains until safe temps are exeeded due to increased Vcore. Example; at 22c Ambient, if a C2D is stable at 3.0 Ghz - 1.35 Vcore - 45c Tcase / 60c Tjunction @ TAT 100% Load, then it may also be stable at 3.3 Ghz - 1.5 Vcore - 55c Tcase / 70c Tjunction @ TAT 100% Load, with highly effective CPU cooling and computer case cooling.
Tools
SpeedFan 4.32 displays all 3 Tcase and Tjunction sensors:
http://www.almico.com/speedfan.php
Intel's Thermal Analysis Tool (TAT):
http://www.techpowerup.com/downloads/392/mirrors.php
Orthos:
http://www.techpowerup.com/downloads/385/Orthos_Stress_Prime_2004.html
Testing
Vcore = Manual
C1E / EIST = Disabled
CPU Fan = Manual, 100%
Computer Case Fans = Manual 100%
Computer Case Covers = Installed
Primary Test = TAT @ 100% 10 Minutes
Alternate Test = Orthos @ P9 Small FFT?s 10 Minutes
TAT will expose insufficient CPU cooling and computer case cooling, or excessive Vcore and overclock. At no other time will a CPU be so heavily loaded, or display higher temperatures, even when highly OC'd during worst-case / real-world loads. After CPU thermal behavior has been benchmarked by TAT, then Orthos or assorted other programs can be used with SpeedFan to observe less extreme CPU temps, while stress testing for system stability. Orthos Priority 9 Small FFT?s simulates 88% of TAT ~ 5c lower. During gaming and applications, Core 0 typically carries heavier loads and higher temps than Core 1.
Scale
The temp scale shown below illustrates the normal ~ 25c Delta between Idle and TAT @ 100% Load, and the typical ~ 15c Delta between Tcase and Tjunction on an example system overclocked with 1.4 Vcore. 50c Tcase and 65c Tjunction are safe and sustainable temperatures.
Tcase/Tjunction
--60--/--75--75-- Hot
--55--/--70--70-- Warm
--50--/--65--65-- N
--45--/--60--60-- O
--40--/--55--55-- R
--35--/--50--50-- M
--30--/--45--45-- A
--25--/--40--40-- L
--20--/--35--35-- Cool
Results
Tcase (Motherboard Utilities) = 30c Idle, 50c Load (SpeedFan: CPU or Temp X)
Tjunction (TAT) Hottest Core = 45c Idle, 65c Load (SpeedFan: Core 0 / Core 1)
Variables
Ambient = 22c
Chipset = 975X
C2D = E6600
CPU Cooler= AC Freezer 7 Pro
Frequency = 3.5 Ghz
Load = TAT @ 100% 10 minutes
Motherboard = Asus P5W DH
Vcore = 1.4
The typical ~ 25c Delta between Idle and Load will vary among systems due to inconsistencies such as Ambient temp, overclocking, Vcore, CPU cooling, computer case cooling, graphics cooling, and software processes. Example; if SETI, Folding, or excessive background processes are running simultaneously with Orthos rather than TAT, then "Idle" could be ~ 40%, and "Load" would be 88% of TAT, therefore, the Delta may be only ~ 10c.
The typical ~ 15c Delta between Tcase and Tjunction can be Offset due to erroneous chipsets, super I/O chips, BIOS releases, driver versions, and motherboard utilities. Intel?s spec for thermal sensor accuracy is +/-1c, so temperatures can be quite accurate on hardware / firmware platforms free of manufacturer's deficiencies. Temperatures which have Offsets can be analyzed, and when corrected, may still be accurate.
Heat Score
The following items will enable users to estimate cooling efficiency, identify problem areas, and visualize how environment and system configuration impacts real-world thermal performance.
...
Parameters
. . .
Troubleshooting
...
Offsets ...
[EDIT .... i better not quote all of this ... for copyright purposes ... read it all for yourself ... deleted]
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