Thermal Paste Questions

[steiney]

Hello All,

I have a few questions about thermal paste. Before anyone MRoogle's me, I have read through the previous thermal paste related threads, and didn't really see an answer to my questions. So...

1. After looking through a thorough procedure manual, I don't feel confident that I could handle taking apart my MBP to get to the thermal paste. Therefore, I was thinking I would take it to an authorized Apple technician since I'm in Gainesville, FL and there is not an Apple store here. Is this something most authorized Apple technicians could handle without a doubt? I really can't afford to have my MBP destroyed.

2. In reference to question #1, how much should I expect to pay for this service, not including the cost of the arctic silver, or whatever paste they use?

3. Should I purchase the arctic silver myself, or let the technician supply it?

4. How important is reapplying the thermal paste, in terms of performance? I don't mean in terms of staying cooler, I mean in terms of speed of the processor and overall computer speeds. I have read that some CPU's underclock themselves when they get too hot, in an effort to save the CPU from burning out.

I think those are all my questions. If anyone can offer answers or advice, I would greatly appreciate it.

Thanks in advance!

steiney

 

[alphaod]

An authorized shop won't do it unless you have issues with your existing set up. Too much of a liability to take apart a working computer.

 

[GGJstudios]

Thermal paste has nothing to do with CPU performance. It only relates to temperatures. If your Mac is not overheating, I wouldn't worry about the paste. Mac CPUs don't underclock to deal with temperatures. The fans spin faster at sustained higher temps and if it gets too hot, your Mac will simply shut down.

 

[steiney]

alphaod: Hmm... well what's your definition of working. Everything seems to be working fine, but sometimes it seems that everything starts to get kind of slow. That may just be because I have a lot of Safari tabs open as well as other memory intesive programs.

Do authorized Apple technicians generally warranty/insure their work? I've only recently passed my Applecare expiration date, so I've never used one before. Although, I can only imagine they wouldn't let the computer out of the shop without testing it to make sure everything is working properly.

GGJstudios: Thanks again. You've helped me with a couple other threads over the past few days. In reference to your comment, I haven't taken any actual temperature readings when the MBP heats up (although I should have), but I can tell you it gets hot enough that it will burn my the skin on my legs if there is not something between the computer and my skin. I don't mean third degree burns, but enough that the skin will be red and tender for a day or so, and hot enough that I can't stand to keep the computer directly on my skin. Is that hot enough to be considered overheating?

 

[GGJstudios]

... hot enough that I can't stand to keep the computer directly on my skin. Is that hot enough to be considered overheating?

No, it's normal.

Install iStat Pro to get accurate readings of your temps, among other things

Your temps are most likely perfectly normal, as searching the forum with MRoogle will reveal:

Macbook Pro Heat Dissipation
2010 Macbook Pro 17" i7 heat question
Heat on my i7 Macbook Pro 15"
Macbook overheating?
My Macbook Pro reached 106 degrees !
Macbook pro heat problem
MacBook Pro Over Heat Issue
Heat on my i7 Macbook Pro 15"
Macbook pro Hot after 10.6.3. Update
Macbook Pro too HOT!!!
My Macbook Pro Runs Hot
Macbook Pro gets really hot when running windows 7
How hot should my macbook be getting?
Macbook Boiling Hot!
Hot 15" i5 MBP!
MacBook Pro Overheating or That's What I Think It Is?
Macbook pro temperature
MacBook Pro heat causing pain in hands
Alu Macbook vs. 13" Macbook pro: Heat & Battery Life
Etc., etc., etc.

 

[Pax]

.... but I can tell you it gets hot enough that it will burn my the skin on my legs if there is not something between the computer and my skin. I don't mean third degree burns, but enough that the skin will be red and tender for a day or so, and hot enough that I can't stand to keep the computer directly on my skin. Is that hot enough to be considered overheating?

As GGJ says your temps are probably normal, but iStat can tell you a lot. It depends somewhat on your model - the newer the model, the cooler the base as Apple refines the design. IMHO bad thermal paste is unlikely to be the cause of your hot legs. It's conceivable you have a fan problem if your Mac is getting really, really hot, but probably your Mac is "normal".

I would suggest getting iStat and uploading a screenshot of it to here. Do it when your CPU is idle, and when it is at 100% load (various ways of doing this, we can tell you if necessary).

I would not get too excited about your thermal paste, IMHO in most cases there is not much wrong with the "stock" paste. iStat will also test your thermal paste to some extent:- at 100% CPU load, if you see a temperature difference of 20-25C between the CPU and the heatsink, then your thermal paste is OK and swapping it won't make a huge difference to temperatures. If the temperature difference is a lot bigger than 25C then changing the paste may be useful.

 

[Pax]

Mac CPUs don't underclock to deal with temperatures.

Are you sure?

The Intel developer documentation says that if the die temperature exceeds Tj,max:- "The Intel Thermal Monitor controls the processor temperature by modulating (starting and stopping) the processor core clocks or by initiating an Enhanced Intel SpeedStep Technology transition when the processor silicon reaches its maximum operating temperature."
(from the datasheet here....
http://www.intel.com/products/processor/core2duo/mobile/techdocs.htm)

There is nothing in the documentation about being able to bypass this feature, it seems to be hardwired into the cores. I don't know whether Apple could do it, it doesn't sound like a sensible thing to do anyway.

So if steiney is complaining about sluggish performance could it not be the CPU down-clocking in this mode?

 

[tatical]

I replaced the thermal paste on my Mid '09 MBP, here's a thread about it. LINK
BTW, the CPU's max temp is now 85 degrees, no higher.
In hindsight, I should have installed Windows through BootCamp to record the temps. I would have gotten more accurate temps (per core temps).

As for you questions, I can't answer 1 & 2.

Q3. Should I purchase the arctic silver myself, or let the technician supply it?
A3. Yes, because the tech may use something else if you don't supply it.

Q4. How important is reapplying the thermal paste, in terms of performance? I don't mean in terms of staying cooler, I mean in terms of speed of the processor and overall computer speeds. I have read that some CPU's underclock themselves when they get too hot, in an effort to save the CPU from burning out.
A4. As far as a MacBook Pro is concerned, reapplying the thermal paste for performance benefits won't have any effect at all. But some CPUs do underclock themselves to prevent thermal damage. MacBook Pros have CPUs that do this.

Read this part of this Wiki article:
http://en.wikipedia.org/wiki/Underclocking#When_used

Some processors "underclock" automatically as a defensive measure, to prevent overheating which could cause permanent damage. When such a processor reaches a temperature level deemed too high for safe operation, the thermal control circuit activates, automatically decreasing the clock and CPU core voltage until the temperature has returned to a safe level. In a properly cooled environment, this mechanism should trigger rarely (if ever).

 

[cluthz]

Are you sure?

The Intel developer documentation says that if the die temperature exceeds Tj,max:- "The Intel Thermal Monitor controls the processor temperature by modulating (starting and stopping) the processor core clocks or by initiating an Enhanced Intel SpeedStep Technology transition when the processor silicon reaches its maximum operating temperature."
(from the datasheet here....
http://www.intel.com/products/processor/core2duo/mobile/techdocs.htm)

There is nothing in the documentation about being able to bypass this feature, it seems to be hardwired into the cores. I don't know whether Apple could do it, it doesn't sound like a sensible thing to do anyway.

So if steiney is complaining about sluggish performance could it not be the CPU down-clocking in this mode?

TjMax is about 100°C for most modern CPUs

 

[Pax]

TjMax is about 100°C for most modern CPUs

Yep, 105 for the later C2Ds, I believe it was 95 for one early model.

 

[jkpark78]

Side question regards to heat - somewhat related i hope.

For people who have i5 and i7, i suppose having a 'cooler' CPU in terms of temp can help with the Turboboost feature since one of the dependent variable is the core temp.. So is it conceivable to say that better thermal paste application which reduces core temp can help with performance due to CPU being able to turboboost?

 

[WardC]

Just a quick question (I am in the dark here):

Is the processor on the MacBook Pro upgradable or is it soldered to the board?

Thanks!

 

[GGJstudios]

Just a quick question (I am in the dark here):

Is the processor on the MacBook Pro upgradable or is it soldered to the board?

Thanks!

Not upgradable.

 

[Pax]

I replaced the thermal paste on my Mid '09 MBP, here's a thread about it. LINK
BTW, the CPU's max temp is now 85 degrees, no higher.

Thanks tatical, that's a great example of what I mean. With your old paste the temp difference between CPU and its heatsink was 39 C, way too high. With your new Arctic Silver it's 21 C. My 2009 C2D MBP has a temp difference almost identical indicating that Apple's stock paste is pretty good in my case. I've seen lots of other Macs with very similar temp differences. I think the paste problem only occurs with a small minority of Macs (bad manufacture? paste ageing?). Of course if you have a 35 W TDP CPU (i5 or i7) instead of a 25 W C2D you should scale the "acceptable" temp difference by 35/25. There will also be minor differences due to different die sizes, but the rule of thumb seems pretty good.

To the OP:- if you have a CD or C2D and your full load temperature difference is close to 20 C, replacing the paste is probably a waste of time & money. If your temperature difference is in the 30s like tatical's was, then new paste is probably a good investment. But it still might not cure your hot legs. (If you have an i5/i7 scale the 20 C to about 30 C)