The Heatsink Guide: Maximum CPU temperature

THE HEATSINK GUIDE: Maximum CPU temperature and maximum CPU power usage

Introduction

This page is there to answer the common question: "My CPU is running at xx degrees, is it too hot?". Here are the maximum temperatures for the most popular CPUs.

Keep in mind that the onboard measurement facilities are often inaccurate and may report temperatures that are too low. This is especially the case with motherboards that use a thermal sensor below the CPU to "guess" the CPU temperature. The temperature values displayed by the BIOS have usually a correction value added, to compensate for this problem - but in some cases this correction value may be too low, or the sensor might not be in good contact with the CPU.

This means: If the maximum allowed temperature for your CPU is 95°C, and your motherboard reports a CPU temperature of 90°C, then you are not on the safe side.

However, this doesn't mean that you should start to panic when your Athlon XP CPU reaches 60 degrees celsius, for example. Most people tend to underestimate normal CPU operating temperatures - maybe due to overclockers bragging with their super-low CPU temperatures in forums.

Also, note that these values are for CPUs that are not overclocked. Overclocked CPUs may run unstable even if their temperature is way below the maximal specified temperature.

What happens if the maximum operating temperatures are exceeded?

If your cooler is insufficient and the temperature exceeds the maximum operating temperature, then this does not mean that the CPU is automatically damaged. With AMD CPUs, you will usually encounter crashes if the CPU is overheated; but these go away as soon as the CPU is cooler again. In the long term, running the CPU at a temperature that is too high may reduce the CPU life, since an overheated CPU is more prone to electromigration - even if it runs stable. With P4 CPUs, the CPU will turn its speed down automatically when it overheats. No damage to the CPU is possible, but the system will get slower while it's hot (which, in some cases, users might not even notice).

If you attempt to operate a CPU without heatsink at all, recent AMD CPUs will usually be permanently damaged within seconds, unless special protection circuitry is available on the motherboard. P4 CPUs will run excessively slow without cooler.

The purpose of this page is to give you a quick overview of typical maximum operating temperatures for common CPUs. In the case of Intel CPUs, values vary a bit; if you need precise information for one specific CPU model, please use the datasheets on the CPU manufacturer's website, or visit Chris Hare's Processor Electrical Specifications page - there, you will find more details, and also data for more exotic CPU types than the ones covered here.

Higher is better here

On cooling-related websites, lower temperatures typically correspond to better products. On this particular page, the opposite is true: The higher temperatures a CPU can withstand, the less cooling is required. CPUs with low electrical power, but high temperature rating can be used with more quiet and more compact coolers. An example for such a CPU is the Pentium-M, which dissipates less than 25 watts, but may reach temperatures of up to 100°C. The worst-case example is the Pentium 4 Extreme Edition 3.46GHz, which dissipates over 110 watts, but may only reach a maximum temperature of 66°C. Obviously, you need a large and possibly loud cooler here.

The actual data:

AMD Athlon, Athlon 64, Opteron, Duron and Sempron

All Slot A CPUs (Athlon classic, Athlon Thunderbird)	70°C
Athlon Socket A up to 1 GHz, Duron up to 1.3GHz	90°C
Athlon "Thunderbird" Socket A 1.1GHz or more	95°C
Athlon MP 1.33GHz or more	95°C
Athlon XP up to 2100+	90°C
Athlon XP 2200+ and faster	85°C
Duron "Applebred" 1.4G and faster	85°C
AMD Opteron	69 or 70°C depending on model
Athlon 64, 64FX, Sempron	Most models 70°C; 65°C for some Socket 939 Athlon 64 models
Athlon 64 X2 (dual core)	65°C

AMD K6 series

All K6 CPUs (166-300MHz) and most K6-2/K6-III CPUs	70°C
K6-2/K6-III CPUs, model name ending with X (e.g. K6-2-450AFX)	65°C
K6-2-400AFQ (uncommon)	60°C (!)
K6-2+, K6-III+, most mobile K6/K6-2 CPUs	85°C
mobile K6/K6-2 model name ending with K (e.g. mobile K6-2-P-400AFK)	80°C

The temperatures specified for AMD CPUs max case surface temperatures. These CPUs do not have an internal diode to measure CPU temperature. The accuracy of the CPU temperature measurement depends on the motherboard; therefore, it is possible that the CPU overheats even though the CPU temperature reported by the motherboard is below the specified maximal temperature.

Intel Pentium III

Pentium III Socket 370 500-866MHz, Pentium III Slot 1 (first generation, OLGA) 550-600MHz, Pentium III Slot 1 ('Coppermine') 500-866MHz	80-85°C depending on model
Pentium III Socket 370 and Slot 1, 933MHz	75°C
Pentium III Slot 1 933MHz	60°C (!)
Pentium III Slot 1 1GHz	70°C for newer versions 60°C (!) for older version
Pentium III Slot 1 1.13GHz (first version)	62°C (!)

Pentium III max temperatures are the maximum temperatures reported by the thermal junction inside the CPU.

Intel Celeron / Celeron

Celeron 266-433MHz	85°C (max. CPU case temperature)
Celeron 466-533MHz (0.25µ)	70°C (max. CPU case temperature)
Celeron 533-600MHz ('Coppermine)	90°C
Celeron 633 and 667MHz	82°C
Celeron 700-850 MHz	80°C
Celeron 900MHz-1.4GHz	69-70°C depending on model
Celeron 1.7GHz and faster	67-77°C depending on model

Celeron max temperatures are the maximum temperatures reported by the thermal junction inside the CPU, unless otherwise specified.

Intel Pentium II

Pentium II (1st generation, 'Klamath')	72-75°C depending on MHz
Pentium II (2nd generation, 2.0V core), 266-333MHz	65°C
Pentium II (350-400MHz)	75°C
Pentium II (450MHz)	70°C

Pentium II temperatures are the maximum temperatures of the thermal transfer plate (on which the heatsink is installed).

Intel Pentium 4, Pentium 4 Extreme Edition, Pentium M

Pentium 4 Max. temperature depends much on model and clockspeed, but no clear pattern is visible. Consult Intel's tech specs for information on your particular model. (Lowest: P4 Extreme Edition 3.2GHz with 64°C, highest: P4 Willamette 1.8GHz with 78°C).	64°C - 78°C
Pentium M	100°C (!)

Intel Pentium D (dual core)

Pentium D 820 (2.8GHz)	63°C
Pentium D 830 and 840 (3.0-3.2GHz)	69.8°C

Note: Pentium 4 and Pentium D temperature specifications indicate the maximum cover temperature, which is typically lower than the temperature reported by the internal thermal diode. Therefore, your system may be running fine even if the reported "CPU temperature" in the BIOS is higher than the temperature specified here. This does not mean that you're on the safe side, though.

Intel Pentium Pro

Pentium Pro, 256 or 512K L2 cache	85°C
Pentium Pro, 1MB L2 cache	80°C

Pentium Pro temperatures are maximum surface temperatures.

Typical maximum power usage of common CPUs and overclocked CPUs

Apart from the maximum CPU operating temperature, the maximum power usage under typical worst-case conditions (thermal design power) is also essential for selecting a suitable cooling system. To find out about CPU power usage, please check out Chris Hare's Processor Electrical Specifications page. There, you will find values for unoverclocked CPUs running at their specified voltage.

How can you estimate power usage of an overclocked CPU based on this value?

The theory behind calculating the power usage for an overclocked CPU is very simple: Power usage is proportional to clock speed, and proportional to the square of the core voltage.

Before we express this as a formula, let's intruduce the following variables:

P_s is the power usage of the non-overclocked CPU
P_o is the power usage of the overclocked CPU
F_s is the clock speed of the non-overclocked CPU
F_o is the clock speed of the overclocked CPU
U_s is the default voltage of the non-overclocked CPU
U_o is the voltage at which the overclocked CPU runs

Here is the formula:

P_o = P_s * (F_o/F_s) * (Uo²/Us²)

A simple example:

We want to calculate the maximum power usage of a Athlon "Thunderbird" 1.33 GHz CPU overclocked to 1.6GHz using 1,9V voltage. From this page, we find out that:

P_s is 70W (max)
U_s is 1.75V

Also, we know that

F_s is 1.33GHz
F_o is 1.6GHz
and U_o is 1.9V

Therefore:

P_o = 70 W * (1.6/1.33) * (1.9²/1.75²) = 99.26 W

Values calculated using this method are not very accurate, since I/O voltage and FSB speed is not taken into account. However, they should be precise enough to help you decide what kind of power supply and cooling you need.

Disclaimer

The information here is provided WITHOUT WARRANTY of any kind. If you are designing a system and need to have accurate information on the maximum temperature of a specific CPU, please rely on the information provided by the CPU manufacturer, and not the information here.

Last update: December, 2004. Future CPU models (even if they are marketed under the same name/with the same MHz) as the CPUs mentioned here may have different thermal specifications.