[TriLUG] Intel processor Temperaturs

[Ryan Leathers]

There is a short answer and a long answer.

The short answer goes something like what John Broome wrote. That might 
be enough in many cases.  The long answer covers several measurements 
you may not even be aware of unless you are designing custom equipment 
or overclocking.  I'll mention a few of these and encourage some further 
investigation for interested readers of this thread.

When considering CPU temperature it is first important to get some 
common basis for describing where temperature is being measured, and 
some consistent terminology to describe the relationship between power 
and heat as these pertain to CPUs.  The main terms to be familiar with are:

Maximum Theoretical Power (MTP) = the maximum amount of power a CPU 
could potentially draw
Thermal Design Power (TDP) = the maximum amount of power your cooling 
system must dissipate
Temperature Case (TCase) = commonly known as CPU temperature
Temperature Junction (TJunction) = commonly known as core temperature
Temperature Delta (TDelta) = the delta between TCase and TJunction
Ambient Temperature = the temperature of the room surrounding the CPU
Case Temperature = the temperature inside the case (or the air in close 
proximity to the CPU)

Let's avoid trying to expound too much on the first law of 
thermodynamics here and just generalize by saying a CPU consumes 
electrical energy as it applies power to its transistors. This act, 
along with the impedance of the electrical circuits causes this energy 
to be dissipated in the form of heat.  Heat leads to instability in 
electrical circuits, so it has to be prevented. There are two ways to 
deal with it. First, use only as much energy as you must. Second, 
provide a cooling system capable of dissipating the heat generated by 
this amount of power.

Manufacturers don't expect you to run their CPUs at MTP and nether 
should you. Instead, they describe expected operational power 
consumption by referencing TDP.  This number is more a categorization 
than anything else. A CPU with a TDP of say 65 might be a good choice 
for a HTPC system using mostly passive (and quiet) cooling. A CPU with a 
TDP of 140 is a good candidate for a more aggressive active cooling 
solution.  However, it is not uncommon when overclocking to exceed TDP 
by 50% or more.

Intel doesn't offer any TDelta specifications for normal operation.  
Instead, they state the recommended maximum TCase at the maximum TDP for 
each part. What does this mean? Basically, if you have a better cooling 
solution then you'll be able to dissipate more heat and therefore 
operate with more power consumption while maintaining a reasonable 
TCase.  This is where we start to get into overclocking and need to 
start paying attention to the specifics of each CPU.

In the specific example of your E7500 the recommended maximum TCase is 
74.1C at at TDP of 65W.  You are within that limit and since this is a 
conservative recommendation you should have no worries whatsoever.  As 
suggested, if you decided to add improved cooling you could bring down 
the TCase value, but this would gain you nothing unless you also planned 
to increase power in order to overclock for faster performance.

Best,

Ryan















On 5/12/10 9:26 AM, John Broome wrote:
> On Tue, May 11, 2010 at 20:54, Ralph Blach<chipperb at nc.rr.com>  wrote:
>    
>> I have a dual core Intel(R) Core(TM)2 Duo CPU     E7500  @ 2.93GHz and when
>> it is idling it runs about
>> 43 C but when I start up VirutalBox, and do a compile the temperature seems
>> to go up to about 68 to 71 C
>>
>> Is this normal?
>>      
>
> So the temp spikes when you're doing a highly CPU intensive task then
> drops when that task is done?  I'd say that's normal.
>
> "Doctor, my hand hurts when i hit it with a mallet, but stops hurting
> when i don't hit it.  Is that normal?"
>