lapped my ultra-120 extreme (pics and temp results)

[graysky]

When my Ultra-120 X and I have to say I'm a little puzzled. The base where it should contact the heat spreader is not smooth at all, it's actually grooved! You can see a scratch which is where I gently ran my thumb nail over the surface; I could feel the rough edges.

Have a look for yourself:


Anyway, others encouraged me to lap it which I've never done before. After wrestling with the idea for a couple of days as well as reading many articles/guides, I decided to give it a go. $20 worth of sandpaper, a $2 piece of flat glass, and 4 hours of careful work (and sweat) later, I was left with a pretty darn flat HS. You can see by the pictures that this particular one was quite concave instead of being flat which isn't good for keeping contact between the HS and IHS of the CPU.





Did it work you're probably wondering. The temp data as measured in speedfan.exe for a ~1 h x264 encode (uses all 4 cores with a CPU load of >99 %). I had speedfan log the temps (which it does every 3-4 seconds) and I averaged the whole data set per core for the 2nd pass of the 2-pass encode (the 2nd pass is the most CPU intensive). Room temp for both experiments was ~23 °C. By the way, I added a constant of 15 to each core in speedfan since it incorrectly displays temps for quads by 15 °C.

System specs: Q6600 @ 9x333=3.01 GHz (stock voltage), P5B-Deluxe in an Antec p182 case.

Before lapping the HS:

Core 0: 66.9
Core 1: 66.4
Core 2: 60.6
Core 3: 60.6

After lapping the HS:

Core 0: 64.9
Core 1: 64.4
Core 2: 59.0
Core 3: 59.4

Delta:

Core 0: 2.0
Core 1: 2.0
Core 2: 1.6
Core 3: 1.2

[dave87]

Not bad at all.

If you had the time and inclination you could probably go to 2000 grit, and lap the CPU core, both of which should give you another couple of degrees drop in temperature

[wja96]

There was a discussion paper written (that handily enough I can't now find) but the gist of it was that if you had good TIM and a micro-grooved heatsink then you could increase the available area for heat transmission by a significant amount if the TIM could be made to be forced into the grooves. Given that Thermalright are pretty good at these CPU coolers, I find it hard to believe they would leave the base of $65 cooler unfinished like that unintentionally. When mine arrives I'm going to give it a month to let the TIM set properly and then see how it compares.

Interesting post though.

[IAmATeaf]

Not exactly the drops I'd thought you'd get but 1 or 2 degrees can't be sniffed at really, could mean the diff between stability or not at overclock.

I see you're in the states and the Extreme version is out there, waiting for it to hit the UK shores myself

[Andy3536]

I work in electronics and with components the piont of having a rough surface is that it creats a larger surface area with the thermal compound and will give you better cooling as the paste gets in to the small indentations. This is why they are supplied with a rough bottom.

[Flewis]

Originally Posted by Andy3536

I work in electronics and with components the piont of having a rough surface is that it creats a larger surface area with the thermal compound and will give you better cooling as the paste gets in to the small indentations. This is why they are supplied with a rough bottom.

But it would seem better temps are achieved with a smoother base. Thermal paste is actually an insulator, maybe thats got something to do with it.

[Andy3536]

Thermal paste is highly conductive, ok it doesn'y match the properties of metals but you would be wrong to think it's an insulator.
In this case it's most likley that the better results were due to the fact that the nickle plate had been removed and the thermal paste was applied to the copper, which is a far better conductor than nikel. It also is'nt a completey flat surface, that last picture clearly shows fine scratches through the copper (although certainly smoother than before)

[graysky]

Originally Posted by Andy3536

I work in electronics and with components the piont of having a rough surface is that it creats a larger surface area with the thermal compound and will give you better cooling as the paste gets in to the small indentations. This is why they are supplied with a rough bottom.

Maybe, but how can you explain the temp decrease I got when I lapped it? I also lapped the IHS on my Q6600 and saw some major decreases in temp. I think what your argument about surface area does make sense, but the data would say otherwise -- at least in my system.

[mrt9888]

What did you use the glass for?

[Agent]

Originally Posted by Andy3536

Thermal paste is highly conductive,

Sorry, but most thermal paste is non conductive, hence why the quite happily splash it everywhere on motherboards and don't worry about in

In the case of something like AS5, its slightly capacitive, but not conductive.

[Agent]

Originally Posted by mrt9888

What did you use the glass for?

Glass / Mirrors are one of the flattest surfaces you can get cheaply

[Flewis]

we were talking thermal properties not electronic

[Agent]

Doh - Must read closer next time

Apologies

[Andy3536]

Originally Posted by graysky

Maybe, but how can you explain the temp decrease I got when I lapped it? I also lapped the IHS on my Q6600 and saw some major decreases in temp. I think what your argument about surface area does make sense, but the data would say otherwise -- at least in my system.

I belive i answered that in my second post.
If you look at your processor in the link, wouldn't you say thats a rough surface?
Was taking thermal properties with the thermal paste, the majority are silicone based and will not conduct electricity but the better ones are normaly electricly conductive aswell.

[Phil_P]

Originally Posted by Andy3536

I work in electronics and with components the piont of having a rough surface is that it creats a larger surface area with the thermal compound and will give you better cooling as the paste gets in to the small indentations. This is why they are supplied with a rough bottom.

Sorry Andy, but I disagree.

Sure there is a larger surface area on a rough surface, but when two surfaces mate (as in this case), far less of that surface area is in contact.

Consider the following crude schematic:

Heatsink
\/\/\/\/\/\/\/\/
/\/\/\/\/\/\/\/\
Processor

and for two flat surfaces

Heatsink
======
Processor

Which has a larger contact area?

The two surfaces should be as flat as possible. In an ideal world they'd both be totally flat and thermal paste wouldn't be needed. However, that's very rarely going to be likely, so we apply a small amount of thermal paste to try and fill some of the voids and thus allow thermal transfer - if the voids were left empty (air), there would be far less thermal transfer.

Your comments above would only hold true if thermal paste was a better thermal conductor than the metal surfaces of the two contact objects, but I highly doubt this is the case.

[Andy3536]

We are not talking large gouges out of the metal work, we are talking 2 surfaces minorly 'roughed up'
This is how i was taught at collage to mount power amplifing transistors! The thermal paste also has somthing to stick to so that when you place the heatsink in possition the paste doesn't all sqeeze out the side.
And your 2 nice diagrams, you would need to ask yourself which one would have the higher surface area if you filled them with a good thermal paste.