My CPU was very out of flat, so the HS contact was extremely poor. I wish I had take a photo when I first pulled the HS up, but basically there was at best 40% contact, a blob on one side then a channel down the center, so two huge areas weren't in contact. Prime95 shot temps up to 78C so I stopped it right away. That's why I took the HS off. Anyway, after that I did some lapping and the temps went way, way down to about 60C. I've since redone the lapping because I realised the edges of the CPU were depressed so I have a lot of the copper underneath the nickel plate showing through and the whole thing is nearly 100% flat. I've also OCed an extra 200mhz, at 3.8ghz my highest temp in a LinX test was 61C. I'd say it's certainly worth doing, and it's really not a big deal. You don't need to use any water, and make sure you only hold the chip on the edges - try not to touch the base at all. Ideally, wear some latex gloves. Aside from that just grab some 800 grit wet-or-dry paper and a nice flat surface like a glass tabletop and have at her.
after lapping your cpu and heatsink did any of you guys experience anything out of the ordinary? did any of you guys end up ruining the cpu or heatsink in any way?
if not then how much decrease in temp could be expected of a WC setup after lapping?
Lapping a CPU is serious business, first off your warranty is gone period so if you do screw it up, you eat it, problems that occur are usually guys that really don't know what they're doing and don't attain a perfectly flat lapping yield, the end result must be perfectly flat, or you can seriously screw it up and have worse cooling than the stock.
I have not ruined any lapping I've undertaken, I'm a firm believer in the process, but I know what I'm doing, and I've lost count at all the lapping I've done, but they all yielded some performance gains even down to chipset heatsink lapping.
Your gains will vary, and most descent water blocks already have a flat finish.
So what are your goals here?
Are you just trying to decide whether to go this route or not as a first timer?
my watercooled loop is actually doing a great job at keeping my cpu extremely cool even under load. i just like to tinker with my computer when i have free time and lapping is just another thing ive been reading up about.
If you're reading up about it, you're starting out right!
Heat sinks today for the most, are manufactured to a lot better finish tolerance than what was available in the earlier overclocking days, in those days lapping a heat sink was almost a must, the bases mostly looked like it had been cut with a circulating saw.
So to get any descent contact you almost had to lap the contact surface, or use a lot of TIM to fill the gaps, once overclockers got more demanding as to the end quality, it forced heat sink manufacturers to get competitive on their contact finish end results so things got much better for us.
So really today lapping falls into the extreme category, especially when it comes to heat spreader lapping, requiring almost zero TIM between the two mirror finished surfaces and usually a 2C to 3C cooler gain on the CPU side itself.
With my Q9550 setup, the heat sink base was on the rough side so lapping it produced a 5C lowering of the temp, lapping the heat spreader yielded another 3c and adding a second 120mm cooling fan gave another 2c drop for a total of 10C drop overall air cooling.
That put me in a range temperature wise of reaching a 4G stable overclock on the Q9550, now in that case, lapping was worth it, and in my opinion lapping is always worth it, unless you forfeit a warranty to do it.