Well, after lapping my HS, I've had this nagging little voice in my head telling me to do the same from the CPU. I did the job with 800 grit sandpaper. Initially, I told myself I'd just buff what's there right now just to see if it's level. After about 30 laps in one direction and 30 in the other direction I discovered I had quite a concave IHS. So I just kept at it. Two 9x11 pieces of 800 grit later paper later I was left with a darn flat layer of copper looking back at me. I finished the job and put a mild shine on it with a sheet of 1000 grit I got from the local auto parts store just for the f*ck of it.
Here are a few pics and the temp. results I got from lapping both my CPU and HS. I would recommend that anyone wanting the best $20 decrease in temps should consider lapping both the CPU and HS.
Hardware details: Q6600 @ 9x333 and vcore of 1.2625V in the BIOS, P5B Deluxe (vdroop modded) cooled w/ an Ultra-120 Extreme (lapped) with Scythe/s-flex SFF21F 1600RPM fan, in a P182 case.
I would recommend that anyone wanting the best $20 decrease in temps should consider lapping both the CPU and HS.
Temp Decrease Data Graph Each temp. point represents an average of data collected over approx. 1 h time period during the 2nd pass of a 2-pass x264 encode of a 720x480 DVD source using a high quality video profile. Data points were logged by Speedfan every 3-4 seconds over this time period. The average CPU usage was >99 % on all 4 cores throughout the experiments. Also room temp was between 20-22 °C.
This is my preferred setup: 8x10 piece of glass on a flat counter top. You can see I cut the sandpaper into a thin strip (about 2-3x the width of the CPU) and attached it to the glass with some tape. The glass is in turn tapped down to the counter top to keep everything immobilized. You'll want to moisten the sandpaper with some mildly soapy water (like 1 drop of dish soap in 1 liter of water), then blot it until you have no pools of water. Remember, if you get water into your chip you're sunk. Then simple hold the chip and gently move it front-to-back. I don't recommend doing circles since they tend to give uneven results. The copper color on the sandpaper is material I just removed from the IHS on the chip.
Remember, you're after a flat chip here so don't push down on it as you lap: let the weight of your hands do it without extra pressure and go slowly so you don't use uneven pressure. After about 30 laps front-to-back, I gently blotted off the chip with a moist paper towel to remove the metal particles I just sanded off, then rotated it 90 degrees and repeated 30 laps front-to-back. Then you'll want to clean off the sand paper (add more water, then blot it damp and repeat). I'd recommend changing the sand paper frequently since it's really doing the work for you. That's basically it. You can start with 400 grit or so and lap until you can't see variations in the surface of the chip (no silver color is often a good indication that you're flat), move up to 600 or 800, then finish off with 1000 or 1200. I did mine entirely with 800 and 1000, it just takes longer with finer grits. Remember, the key is FLAT, not shiny. I would recommend that you do NOT polish the chip with a metal polish since you'll leave behind a residue that will hurt your heat transfer.
You can test the flatness at any point during the lapping process by carefully placing a razor blade across the surface of he chip and looking at the area where the razor meets the chip. Now position your eye so that you're level with the chip and pointing at a light source (a lamp will do nicely). Do you see any light coming though? If so, keep at it. Another test you can do is to take a black sharpie marker and make about 9 dots in a 3x3 grid on the surface of the IHS. Lap about 5 times, rotate, and do 5 more. Now look at the dots... did they wear off evenly? If not, keep at it. You can also simply draw an "X" from corner to corner on the chip and do this as well. Again, you'll looking for even wear.
Oh, I also thought I'd mention that before I lapped the chip, I had a pretty big difference in core temps when loading with prime95 or 2x orthos: up to 6 degrees C (sorry I don't have a screenshot of this). Lapping the chip REALLY evened-them-out as you can see from the coretemp numbers after the IHS and base of the heatsink were lapped (stressed using prime95 v25.3):
The table I showed above was not based on prime95 or orthos, it was based on x264.exe which is a video encoder. It is good at using all 4 cores, but not as efficient as prime95/orthos which explains the differences in temps from that table.
Thanks all. If you have a steady hand, and you're careful, there is no reason why anyone can't do this.
The lower temps can either translate into nothing (i.e. keep the same speed and enjoy the mental effect of the low temps) or you can trade the lower temps for MHz in the FSB.
True... I don't want to jinx myself by saying this, but have you or do you know anyone who needed to invoke a CPU warranty? In the past, I bought "white box" CPUs because they were cheaper and didn't come with the factory HSF that I usually got rid of anyway.
Originally posted by: Kromis
I don't even know what lapping is so...
I'm not even gonna ask!
basically he used sand paper to smooth out the surface of the IHS for better contact between it and the heatsink; it's the same thing people look for on the contact area of a heatsink. see how his cpu is reflective? that means it's smooth.
Originally posted by: lopri
That's some job! The results are even more impressive. Wish I had a gut (and skill) to lap my CPU.. Thankfully it's not too hot.
It was fun. There is no skill to it really. I'm sure you can do it.
Originally posted by: Kromis
I don't even know what lapping is so...
I'm not even gonna ask!
basically he used sand paper to smooth out the surface of the IHS for better contact between it and the heatsink; it's the same thing people look for on the contact area of a heatsink. see how his cpu is reflective? that means it's smooth.
Originally posted by: PhoenixOrion
For all the newbies reading this thread, please take a picture of your IHS so you have a record of the serial number/model number..................before lapping it off.
It's also a good idea to take pics during the process so you have a record of your work. Recording your temps before/after is a good idea too.
good tut...now i bought some 800, 600, and 1500 grit sand pap and started my thing...first i used both sheet 11x9 of the 600 grit and i almost didnt get all the nickel plating out, then i went to the 1500 grit paper...however there is some nickel at the corners, im not sure if that is fine or not....then i went to the HS and tried some of the 1500 grit left...put it back together and even with a new chasis, CM Stacker 832... and temps were the same as before... 43C and 41 at idle.... i will buy thicker sand paper and try again to see if i can get those corners off....then i will do same to HS since its not completely lapped...thanks, i will add pics when i get home....and yes, anyone can lap, its not that hard
I might be wrong but from my study of optics in university physics, surfaces that are reflective actually have zillions of tiny scratches in them. Hence they are not "smooth," and that is how you are able to achieve reflectiveness with something coarse like sandpaper.
By lapping your IHS you flatten it but in terms of the final grit you use, I'm sure there is an optimal grit that is a function of the type of thermal paste you use. Essentially you are forming little grooves in order for the thermal paste to flow into and form a proper layer. It would be interesting to see if anyone did an experiment where they took a few identical heat sinks and processors and tested different grit finishes.
Well I love reading this stuff and seeing great results.
OK I am going to break down and try this myself. I currently have a Q6600 G0 and with my new Ninja Rev B No matter how I set the HS or type of fan or which direction the fan(s) sit. I am getting HUGE differences in temps between cores when running 2 sets of Orthos set to the diffrerent cores of course
Anyhow my question -- someone had said... if you get water on the CPU... you're sunk. In other words when you are rubbing it against the sheet of sand paper, which will be mildly wet on the surface, is there any special way to hold the CPU or shield it or prevent any moisture at all from getting on the other surface. I am just worried that when working no matter how careful you are you might get some sort of debris or filings or anything on the exposed critical part that would be facing up.
Any suggestions? Or it really is not an issue as long as you are careful?
From this graph, my take is that the two cores inside the package are bonded to the IHS differently. One having a better thermal connection than the other.
I realize this is a 6-mo old thread and may have already been discussed.
Thanks for the post, best explanation of lapping I've seen yet.
Hermit
__________________
Living Off-the-Grid Solar Electric on 3KWH per Day
finished lapping my Q6600 (with pics and results)
