XP-90 Odd Base Finish

[Sadistic]

While installing an XP-90 I ordered for my friend I noticed the base had a series of spiral machine grooves (concentric circles which came to a point about the size of a needle point) which made an audible noise when you ran your fingernail over it. Im told this sink is completely nickel plated. I went ahead and used 1500 grit paper and began to lap it down. The spiral groove design never went away and the copper underneath (or what appeared to be copper) began to expose on the corners of the sink. When we started the reflection of text and a coin was blurry, when I finished you could clearly see the features and read text. I got worried when I started seeing the base exposed so I opted not to finish up with the 2000 grit. We just put down a thin layer of AS5 using a single edge razor blade, alcohol'd the base one last time and mounted it to get the "break in process going".


Does anyone think I should have kept going or did I lap to far?

[bluegreenshxt]

what do your temps tell you? ;)

[Sadistic]

Well hes not past the break in point. He switched from the stock P4 fan to the XP-90 with a 92mm Tornado and AS5.

His chip is a P4E 3.0Ghz. It was running 63C core and 33C ambient prior to the heatsink swapout(keep in mind his computer room where im at right now is a toasty 82-83F)

After making the swap his ambient is around the same (due to the room temp) but his peak core under Prime95 is 52C.

Unfortunately, we never did actually mount the stock non-lapped XP-90 up and Prime95'd it to see if the lap job was a success. Also, contrary to the instructions on the AS5 site, I chose to put a rather small dot on the heatspreader and manually spread it around to the size of the core underneath using a single edge razor.

Im sorta questioning myself on the decision to lap and how much AS5 to use :/

p.s this is the first tornados either of us have ownd or heard. The both of us are still doing "double takes" at just how loud they are. He shopped for new headphones today to counter the noise, and Im slowly adjusting :cool:

[bluegreenshxt]

might want to reapply the as5...if you spread it out too thin it may not be contacting properly...if it wasnt perfectly flat you'd might have air bubbles in it...but it shouldnt be too bad...i guess you could experiment and see which method is better :p

and dayum...those p4's are hot...erm...only temperaturewise :cool: :p

[Sadistic]

The impression I got was the flatter the base on the HS the thiner the AS needed. Im fairly certain the lap job was smooth since I didnt run into a single snag (not enough soap on the paper and the sink digs in) like I did while lapping my 947U.

We'll see. Im hoping after a few hundred hours of heatup and cool down the temps will drop a smidge more. If not ill go ahead and have my friend reclean and reapply. Do you think I shoulda kept going on the lap and sanded untill the nickel coating finish on the bottom was gone? Or was I right in stopping when I did?

[bluegreenshxt]

well direct copper contact to the core will give you better temps (how much i cannot say...could be 0.1 degrees..could be 1 or 2)...providing that heatsink maintains good contact on the core...

[Sadistic]

Anyone else out there with an XP-90 whose lapped it or had these same visible machine marks on the bottom?