Should an Active Heatsink be Hot?

[mike breck]

Many times on these forums I have read that the way to check if your HSF plus paste is working effeciently is to feel the heatsink.

It is suggested that if the heatsink is not hot then that means the HSF is not working at optimum effeciency.

But is this right?

You would think that if the HSF was doing a good job then the heatsink should be cool.

My Thermoengine heatsink runs cool all the time and the temps are very good.

The logical extension of this could be that the temp of an active heatsink cannot be used to determine if the HSF arrangement is working effeciently or not.

Of course, it could be my experiences with HSFs have been unusual and that other makes and models have different criteria for establishing working effeciency.

I would like to hear the views and experiences of of other members.

[TEEB]

This a very good point. I have often wondered the same thing. My heatsink is about the same temperature as the metal on my case. I also subscribe to the theory that if the heatsink is doing it's job then it should be cool. If it was hot then the heat is not dissipating as fast as a cool one.
I would love to hear a definitive answer to this one!!

[Alfie]

The general consensis is that if a heatsink feels warm to the touch,heat is being passed on to it,if it's cold to the touch,heat MAY not be dissipated.
If feeling the heatsink,one should feel towards the base,or if possible the actual base,if it's warm heat transfer is taking place,if it's cold...

[mike breck]

Thanks Alfie.

So based on what you say, there may then be a few different scenarios.

I therefore submit the first draft of my "Kamikaze" theory of analysing CPU temps. I call it "Kamikaze" because I look forward to it being shot down in flames...

Allowing for slight differences in HSF models and average room temp of 21c/70f:

IF YOU HAVE LOW CPU TEMPS and...

1. The base of the heat is cool or slightly warm then the HSF is working effeciently.

2. The heatsink feels warm and/or the warm section extends further up the fins of the heatsink then the heatsink is having to work a little bit more and may benefit from a faster fan. Especially, if you intend to overclock.

3. The whole of the heatsink is hot which may mean it is just coping and no more. A more powerful HSF is needed.

IF YOU HAVE HIGH CPU TEMPS and...

1. The base of heatsink is cool. Very little heat is being conducted. Get rid of the pad and use thermal paste. If you have used paste, then you may have done it incorrectly or used too much.

2. The base of the heatsink is slightly warm or warm. It may be that not enough heat is being conducted and or dissipated. Use or redo paste. Add fans to improve air circulation in case. If that doesn't work get a more powerful HSF.

3. The heatsink is hot. Heat is being conducted but the HSF is may be struggling to cope. Add case fans and/or get a more powerful HSF.

Ofcourse, the unknown variable for me is I don't know how warm or cool other HSF units are at maximum effeciency.

I look forward to the first shot....

[Alfie]

Copper heatsinks get warm and run even hotter when the computer is turned off,aluminium heatsinks tend to dissapate faster.
If your temps are low,the heatsink is doing it's job,if it's high it's not.
If the temps are very high(60c+)the heatsink is on backwards,not connected properly,or someone forgot to remove the clear tape off the pad.
Duron's tend to be harder to cool than Tbirds(smaller slug)
When reading reviews,see what the ambient temp is (room temp),don't expect to get the same results,especially during summer monthes and your room temp is over 75f.
Feeling the base is only a way to see if any heat transfer is taking place and a start at trouble shooting.
A instant read thermometer,can also be used as a troubleshooter.
The best way however is the use of thermisistors,this will give you an independant temp monitoring and is accurate to +\- 1c

[Jenni]

A friend called me not too long ago. She was given a computer and was having problems with it, IE constant lockups and crashes. When she told me what was going on, I told her that I was pretty sure that it was a Cryix processor that was overheating. She brought it over, I opened the case, and lo and behold, a Cyrix PR200 with what had to be the smallest HSF combo I have ever seen. I've seen 486's with HSF's bigger than that thing had on it. The HS was big enough to cover the chip, but the fan was about the diameter of a quarter! Needless to say, after running a few minutes the HS was so hot it almost couldn't be touched. So I told her a place to get a new HSF. Anyway, I guess she didn't believe me, her stepmother told me that she "didn't want to spend any more money on that computer" ( she got it for free!!) so she, GET THIS, ordered a new one online!!! Just to run AOL with---she doesn't want to spend $10 on a HSF, so she buys a new computer??? Her $10 investment in a free computer would have been more than enough to go online with! And I didn't even charge her anything!

[glc]

Jenni: Actually that may have been a smart move - the PR200 has to be the most unstable CPU ever made, hot or cold.......

[Jenni]

Oh, I don't doubt that at all. But I do think it would have been fine for running AOL with a bigger HSF. I have another friend that had the exact same problem, Cyrix PR200 that was overheating, and she has been using it just fine for months since I put a bigger HSF on it for her. I mean, AOL crashes just fine all on its own, so your CPU doesn't really matter.

[mike breck]

I think I'll just go with the minimilist approach.

Temp low - HSF good. Temp high - HSF bad

[Jenni]

Mike, the better question to me would be: at what temperature does a given CPU qualify as "running hot"? Based on the number of "hey, my CPU is running at xxC, is that too hot?" posts I see here all the time, nobody knows for sure just exactly how hot "too hot" is. And, how accurate are those BIOS monitoring stats? I know the Windows monitoring utility that came with my Aopen board wasn't very accurate at all, it said my CPU was running at 77F. Now the BIOS monitoring and Sandra both put it at 96F most of the time. But, Sandra also says my "mainboard temperature" is 140F, and that I should power down immediately!

[TEEB]

That is the question I would like to know the answer to. One member(I forget who) stated that most people say that 80 C and over is hot. Yet some have posted higher temps and their CPU's were still running. Another way of asking it is what is a *safe range*? My system runs at 57 C when it's all closed up. They say that's too hot. But, when I put my finger on the heat sink it's just *warm* to the touch! It doesn't seem excessive to me!!

[Alfie]

The bottom line is the cooler your cpu is the more stabile it tends to be.
AMD has given a top temp of 95c(this is the internal temp of the cpu.
If one considers water boils at 100c,we see the cpu is rather tolerant.
However when the temps go over 60c and are sustained,some flakiness MAY occur.
The price of a cpu not too long ago could run as high as $3,000,it was then discovered that by keeping the cpu cool,it's life expectancy could be greatly increased.
With prices like that,you definitely wanted to protect your investment!
In modern day computing,it's been discovered the cooler the cpu,the better your chances are at overclocking it,hence the onslaught of more advanced heatsinks and fans.
If one were to run their cpu at stated speed,a stock heatsink would suffice.
Yes,they may see temps at 50c and higher,but this is tolerant.
It's when you start stretching the cpus limits that temps start playing a big roll.
Let's take a Duron (harder to cool than a Tbird,smaller slug)lets say a 800mhz,rated to run on 1.6v,standard TiaSol heatsink,temp range 40c-50c,runs like a champ.
Now we want to overclock it,set the speed to 1,000mhz,voltage 1.85,with our standard heatsink,we watch the temp increase,now hitting the 55c-65c range,flakiness may set in,system crashes,bsods,etc.Protection errors and generally wierd things.
We now have a choice,improve the cooling,or reset it to it's defaults.
Opt for better cooling,cpu 1,000mhz. voltage 1.85v temp range 35c-41 c.
All is well,all is cool
By feeling the heatsinks base,we simply can tell if heat transfer is taking place.
The temps reported by bios and monitoring software are the estimated temps of the cpu itself,not the heatsink.
By adding 10c-15c to the temps reported,we can roughly tell how hot the core of the cpu is.
Hence when we see temps of 60c+ and add our 10c-15c we see temps of 70-85c actual core temps,if the cutoff point is 95c and at that temp flakiness WILL start and even possible cpu failure, we see as one approaches it, instabilty will PROBABLY set in.
Some people have reported problems at the 55c range,while others seem to operate fine at higher temps.
It's safe to say each cpu has a uniqueness to it,some being more tolerant than others,some more overclockable than others,etc
So in turn,no one can put a blanket over the whole thing,if your computer runs fine at a higher temp,don't worry about it,cpus these days are cheap.
However,if you want to keep it a while,overclock it and generally abuse it,KEEP IT COOL!

[mike breck]

Jenni: Considering the amount of discussion and debate on this subject, AMD (my original ? was really concerning Athlons) should clear this up themselves.

I don't think quoting a top temp of 95c is good enough. Why doesn't AMD state what they think is a good and safe temp for each model and speed of CPU?
Perhaps it's just as well they don't manufacture explosives!

Alfie: Thanks for all the information. Very interesting and informative.

My original point was this

It is suggested that if the heatsink is not hot then that means the HSF is not working at optimum effeciency.

But as you say yourself, feeling the base of the heatsink is only an indication that heat transfer is taking place. But, from this alone, the non-expert cannot determine the effeciency of the heat transfer.

Different Heatsinks will have different temps when working well. As you reminded me, Copper should feel hotter and Aluminium cooler. So the temp of the heatsink when working well will be determined by make, model, metal, fan, CPU speed, pad, paste, room temp etc.

So only someone with a vast experience of working with particular HSF/CPU combinations would be able to tell if heatsink felt the right temp in any given situation. A beginner, posting on these forums, would not.

So telling someone that "if the heatsink doesn't feel hot then it isn't working properly" may not be right in all cases.

Perhaps asking "what HSF are you using and does the heatsink feel cool, warm, or hot at the base" might be better. Then forum members with knowledge of that particular HSF/CPU combination could give advice on how hot it should feel when working well.

[Alfie]

Here's an interesting read as to what temps are acceptable.
http://www.overclockers.com/tips400/