How does it work?
Core Temp makes it easy for you to monitor the temperature of any modern x86
based processor. The program supports processors from all three major
manufacturers; Intel, AMD and VIA.
Intel processors starting with the "Core" series all the way up
to the newest Core i7, including all the derivatives.
AMD processors starting
with the first Athlon64 and Opteron processor series, all Phenom and AMD's new
APU are supported.
VIA processors starting with the C7 generation of
CPUs, including all the derivatives based on the C7 architecture. All of the
Nano based processors are supported as well.
The temperature readings are very accurate as the data is collected directly from a Digital
Thermal Sensor (or DTS) which is located in each individual
processing core*, near the hottest part. This sensor is digital, which
means it doesn't rely on an external circuit located on the
motherboard to report temperature, its value is stored in a special
register in the processor so that software can access and read it.
This eliminates any inaccuracies that can be introduced by external
motherboard circuits and sensors.
This is how the program works:
Intel defines a certain
Tjunction temperature for the processor. This value is usually in the range between
85°C and 105°C. In the later generation of processors, starting with
Nehalem, the exact Tjunction Max value is available for software to read in an
MSR (short for Model Specific Register).
A different MSR contains the
temperature data. The data is represented as a Delta in °C between current temperature and
So the actual temperature is
calculated like this 'Core Temp = Tjunction - Delta'
The size of the data field is 7
bits. This means a Delta of 0 - 127°C can be reported in theory. In fact the
reported temperature can rarely go below 0°C and in some cases (Core 2 - 45nm
series) temperatures below 30° or even 40°C are not reported.
AMD processors report the
temperature via a special register in the CPU's northbridge. Core Temp reads
the value from the register and uses a formula provided by AMD to calculate the
The formula for the Athlon 64 series, early Opterons and
Semprons (K8 architecture) is: 'Core Temp = Value - 49'.
For the newer generation of AMD processors like Phenom, Phenom II,
newer Athlons, Semprons and Opterons (K10 architecture and up), and their derivatives, there
is a different formula: 'CPU Temp* = Value / 8'.
*CPU Temp is because the Phenom\Opteron (K10) have only one sensor per package,
meaning there is only one reading per processor.
VIA processors are capable of
reporting the temperature of each core. The thermal sensor provides an absolute temperature
value in Celsius, there is no need for any conversion or manipulation.
The Tjunction or TjMax temperature on VIA chips is
usually between 70 and 90C. 90C for the mobile and low power versions and 70C is for
the desktop variants.