M6700 Heatsink swap/repaste

I'm starting to wonder whether the difference in core temps could be due to the physical location of the cores, whether they are close to another core, the IGP or the I/O controller.

 

Well, that's a bust.

Before upgrade

Stock single-pipe heatsink
Already repasted once by a tell tech while swapping the motherboard, no attempt to clean before re-pasting.


Idle, all cores at < 5% running light office work, 1.2-1.4 GHz

After a good while
Core 0 at 49-51
Other cores around 45-49


Under load, all cores at 100% running video encode, 3.4 GHz

After 2 minutes
All cores at 82 +/- 2

After 5 minutes
All cores at 84 +/- 2


After upgrade

Brand new dual-pipe heatsink (like those used for "XM" CPUs)
Cleaned off old thermal paste from CPU, using the paste included on new heatsink


Idle, all cores at < 5% running light office work, 1.2-1.4 GHz

After a good while
Core 0 at 50-52
Other cores at 47-51


Under load, all cores at 100% running video encode, 3.4 GHz

After 2 minutes
All cores at 86 +/- 1

After 5 minutes
All cores at 86 +/- 2


Bottom line

Temperatures are up a few degrees with the new heatsink and stock paste.

Thinking I might re-paste myself and see what happens. What's everyone's favorite thermal paste to use?

 

Interesting.

I wonder if all the data historically and presently combined have led the manufacturers of heatsinks to know that up to certain point the heat dissapation doesn't occur as expected with copper. Hence the differences in heat pipes to processors.

Not that I know anything about this except that on the lower drawing units only one pipe is required to stay within the specification.

 

Thanks for the how-to guide, will have to see how it differs from my recently purchased M4700.

Question:
I just took apart my old Sony Vaio laptop, cleaned the hell out of it and managed to drop running idle temps from @55 degrees celcius to @40 degrees, a whopping 15 degree plunge (granted old thermal paste was brittle and poorly applied, and fans were half clogged with dust).

Is it worth it to go through the trouble of repasting on the new M4700, or should I break in the machine for a few months first? If I could get close to 10 degree drop then a repaste now would be in order ;-)

The reason I ask is that while the Dell machine is generally whisper quiet, when the fans do come on, they come on with cooling intent, which is to say, don't stop until CPU temp is literally 35 degrees celcius (a bit too conservative, IMO). Add to that the fact that Nvidia Quadro graphics with multi-monitor setup requires max GPU (i.e. cannot force downclock as one could do in the past with Nvidia cards), we have more heat in the system.

To put in perspective, my idle temps are in the low 50s for CPU and GPU, and I would think that low 40s idle temps would be possible with "correctly" applied thermal paste in a brand new machine with all BIOS power saving options selected.

Finally, not sure what its like on the Windows side of the fence, but on Linux (Fedora 18), one has no (supported) control over fan settings and, as mentioned above, Nvidia Quadro dual monitor setup is impossible to downclock.

Salient bits of my setup:
3840QM
SSD X 2
Nvidia K1000

These Precision workstations are absolute beasts, BTW ;-)

 

IC Diamond. This was my first time using it. It is quit a bit more viscous than other thermal pastes but it dropped my temps on the "hot cores" (under load) over 10C. One thing to be aware of - it will scratch the surface of your CPU (it does have crushed diamonds in it after all).

 

IC Diamond is good, Arctic cooling MX-2 and MX-4 as well as are a ton of others. Just go with a reputable brand and you'll be good to go.

Strange that the bigger heatsink is giving you higher temps, there is no reason I can see that would decrease the heat transfer with the extra heat pipe. Unless your fan is actually running at lower speeds. It is possible that you are no longer hitting the temperature where the fan kicks in at higher speeds. The thing is that if 84C was your absolute max, then there should be no change in fan profile, if you got a small spike in temps, it is possible that you had the fans reving faster.

 

I made sure to measure the idle speeds while the fan was at the lowest level for a while. As for under load, it was always running at the highest speed.

I'll investigate the IC Diamond, probably will sit on it for a couple of weeks though.

 

I'm a bit surprised by this, but I'll roll with the data and think of possible explanations . I gotta ask though, did Dell replace the motherboard with the whole heatsink attached to it? If they didn't, the tech probably repasted your previous heatsink.

 

Correct. During the motherboard swap, the heatsink was removed and repasted. While the Dell tech did it quickly, it's quite possible the new pasting was better than whatever is on the stock heatsink. I don't have any data from before the motherboard swap to compare.

 

Here you go. Set it to Celsius.

1st Test
Indoor Ambient Temp 73F. Machine off for one hour before starting.


2nd Test
Indoor Ambient Temp 73F. About 25 Mins after first test.

I'll run two more tomorrow Outdoors during peak of day on a glass table.