"The Equalizer" by g_f

[gone_fishin]

It hit me in the face. What I observed (large goop around the core) is not a bad thing. What do I mean? The IHS is thin and pliable. So? the portion above the core is stiff because of the core underneath. So? The thicker application of goop is forced away from the center because there is no give there but as it collects around the core from the mounting presure, the unsupported region around the core will give way. If you follow then a thicker application will result in a thicker collection of goop around the core area and bend the IHS under the mounting presure and as a result apply more force to the PCM material under the IHS.
Am I deluded or did that make any sense?

[BillA]

5 x 5 (loud and clear)
thats how it works

- but the area away from the die is not doing much at all
get used to it, many more IHSs on the horizion

[gone_fishin]

Originally posted by unregistered
5 x 5 (loud and clear)
thats how it works

- but the area away from the die is not doing much at all
get used to it, many more IHSs on the horizion

The area away from the die is not transfering any significant amount of heat, agreed, but it is needed to apply presure to the core. Lay a piece of seran wrap over a solid surface, then grap the edges and pull down. The seran wrap stays at the same level over the solid surface but force is still applied downward even if the surface does not move.

Now a thinner material over the core should be a good thing no? And what about the copper exposed instead of the etched plating?

[N8]

Originally posted by unregistered
g_f
sorry to hop back into the P4 sanding subject, but several of you might be interested

the IHS is the Marketing Dept.'s name for a CPU protective cap
made of thin copper, nickel plated after forming for corrosion resistance (discoloration), adhesively bonded to the package perimeter with epoxy

-> the protection is afforded by the relatively stiff perimeter which is lower than the central area and serves to limit the application of off-axis (angular) loading of the CPU

the 'IHS' is too thin to contribute significantly to lateral heat dispersion (run the calcs - Waterloo),
and is designed to deflect under the applied load from the spec hsf to a 'flat' plane

-> under the 'IHS' is a PCM insert, there is a 40°F offset due to the IHS plus PCM
(Intel is willing to take this ‘hit’ for the protection afforded by the ‘IHS’)

this info from an ex-Intel thermal engr with whom I have some dealings

now consider what the effect is of sanding 'off' that bump in the center of the IHS
-> instead of a somewhat concentrated load over the CPU area, the load is distributed and born also by the edges that were intended merely to stabilize the hsf
-> the compressive load on the PCM is significantly reduced and . . . .
stretch a bit, read up on what PCMs need to work well, temperature and . . . pressure !!

I’m sure everyone will report lower CPU temps after sanding,
because we see that which we wish to see
- no one here read the article about the DIYers who know more than Intel ?

mercy, tough crowd here

Valid points. I don't (didn't) see the IHS flattening out in my case before I decided to lap it.

I started out with my 1.8a and the stock Intel heatsink. I cleaned off the TIM material on the stock Intel heatsink and used AS3. I believe one of the reasons for Intel making the 'peaked' IHS is as Bill mentions, to lessen off-axis loading, and also because they intended that their heatsink and TIM (thicker than paste) would be used. Even with the TIM removed from the stock Intel heatsink, I had to use a LOT of pressure on the stock attachment arms (pretty idiot proof design, BTW) to lock them in place. My mobo did NOT look good bent like that once the pressure was on the heatsink. I have never seen a mobo bend to that degree. I reseated it several times, but it was the same each time. I said, "screw it, must be what they intended", and fired it up. I ran it for about 4 days or so with the stock heatsink, as overclocked as I could get it to run RC5. The thing ran pretty hot, 55-70 C. Remember, this was with an extreme amount of pressure on the CPU/heatsink.

When I started testing the CPU with air cooled water and then phase change cooled water, I took the stock Intel heatsink and lapped it. It was very high in the center as well. It took an incredible amount of lapping to flatten it out. Between the rounded IHS and the rounded stock Intel heatsink, there was no way to side load the damn installation since they were basically two rounded surfaces. The AS3 interface pattern showed that they were only touching at the center, no flattening had occurred, at least not in respect to the whole IHS. I re-installed the stock Intel heatsink after lapping it, and the mobo bending was not as bad, although it still looked more bent than I liked. I ran it for several days again, and temps were better, but not by much. Could be just the fluctuation in room temps.

When my MCX4000 arrived, I decided to check the cpu itself for flatness, since the MCX4000 had a very flat base and the mounting method would suit a flattened IHS better. After seeing how un-flat the P4 was, I decided to lap it. This was not a hasty decision, and I thought through some of the reasoning that has already been brought up by others in this post. Seeing as how hot I had run the CPU and the amount of pressure that had been on it, I didn't see how the IHS could flatten out any further, if it was even supposed to. I re-tested with the lapped Intel heatsink, and temps were still about the same. This would support Bill's statement that the IHS does not substantially affect lateral heat dispersion, which makes sense anyway, since the core is fairly small compared to the thickness and dimensions of the IHS. Having both the IHS and the heatsink peaked at the center of the heatsource is a good design consideration 'for the masses.'

Since we are not 'the masses', but enthusiasts seeking better cooling, we modify and consider design advances to enable better cooling. Since I knew I was going to be installing a flat heatsink with mounting through the 4 mobo holes, AND I knew I had 'run-in' the cpu with a very high amount of pressure and heat, AND I have years of professional lapping and polishing experience, I felt comfortable lapping down the IHS, since I felt it was at it's final resting place. I did not do this solely for cooling reasons, but also for the amount of bending that my mobo was under. I did not like it bent like it was, and the only thing left was to flatten the IHS, which was very high in the center still.

Now with the MCX4000 and a quiet 80 mm fan, the P4 is running a full 10C cooler than with the stock Intel heatsink while under full load. Did the IHS lapping do anything? Possibly a degree to two better cooling, but in my case, my mobo is not under a huge amount of stress anymore. Maybe I just got one of the thicker outliers to the variation of PCM thickness. I don't know how much variation Intel has in this application of the PCM.

As far as recommending lapping the IHS for cooling purposes? I don't think it really does that much to help cooling, and I wouldn't recommend doing it unless you have some additional considerations or reasons. In this respect, I guess I was a good guinea pig.

[BillA]

N8

given any thought to removing the IHS ?
(I'd love to get a 'handle' on that 40°F number)

[N8]

Yea, I have thought about it. It will have to wait until I can get a C1 stepping for under $200. Maybe in a month or two. That way I can experiment on this 1.8a.

I am in the middle of renovating a house to move into right now, so I don't have any spare time until mid- December or so. I have to get as much done to this house before it starts to get too cold or snow too much. Managed to get our first house through a closed bid auction/bank repo. Needs a lot of work though.

[BillA]

ah, the landed gentry now, eh ?
congrats

PM me or something when you do it, am interested - but not always here

[gone_fishin]

Here is another view of these first and second stages. You can see the nozzle and gasket arrangement. The central gasket is placed at the proper depth with a shelf milled into the second stage.

[gone_fishin]

Further additions to my development page.
Notice the very center of the bp and also the central nozzle extrusion.

[dream caster]

Originally posted by unregistered
one would have to speculate about the P4 tolerance stack, I've no info like that

PCMs 'overheat' and then take their 'set'' on the first cycle, or several depending
in any case I would think the higher the center, the better;
for thats just where the pressure is desired

wish I could lap like N8

He is a profesional of lapping, look at his web pages.