XP120 carp surface finish

ChrisLX200 · 13 Mar 2006 at 18:06

Anyone else had a close look at the base of their XP120? I was shocked to see how *** awful the machined finish was. Deep curved machining marks where is was milled leaving nothing but a few ridges to contact the chip. No wonder mine never worked particularly well even using AS5. I just spent the last 2 hours lapping it down to flat - had to take all the nickel plating off to do it.

stigggeh · 13 Mar 2006 at 18:09

ChrisLX200 said:
Anyone else had a close look at the base of their XP120? I was shocked to see how *** awful the machined finish was. Deep curved machining marks where is was milled leaving nothing but a few ridges to contact the chip. No wonder mine never worked particularly well even using AS5. I just spent the last 2 hours lapping it down to flat - had to take all the nickel plating off to do it.

how much difference has it made ?

IzaLearnin · 13 Mar 2006 at 18:10

Yes I had a warped base on my xp120 although the surface was smooth. Got a far better contact once lapped. The ihs on my opty was far from flat and had poor contact with the core so I whipped it off and changed to the Evo, dropped 10c off load temps.

ChrisLX200 · 13 Mar 2006 at 18:17

stigggeh said:
how much difference has it made ?

I'll let you know when my new Opty 170 arrives tomorrow... It sure can't be any worse than it was. I didn't do anything clever - just a piece of flat steel and a sheet of ultra fine emery paper, followed by Autosol to polish.

ChrisLX200 · 13 Mar 2006 at 18:22

IzaLearnin said:
Yes I had a warped base on my xp120 although the surface was smooth. Got a far better contact once lapped. The ihs on my opty was far from flat and had poor contact with the core so I whipped it off and changed to the Evo, dropped 10c off load temps.

I might risk doing that myself if this doesn't work. A 10deg drop is ** impressive!

IzaLearnin · 13 Mar 2006 at 18:40

Your 170 dual core is going to run hotter than my 146 so don't expect miracles! When I compared my cpu temps with others on here it led me to believe the ihs had poor contact with the chip and so it proved, others have done the same but not seen much of a change in temps. It is a gamble as resale value will be affected, I only paid £116 so I was not concerned with selling it on - this is a keeper!

Dup · 13 Mar 2006 at 19:01

Fine went and dry + T-Cut + Rubbing compound = lapping heaven. Good for ye old Mr Winky arm

Big.Wayne · 13 Mar 2006 at 19:15

In my earlier days of overclocking (and when really bored!) I did a bit of lapping, used wet'n'dry sandpaper in various grades all the way up to about 1800grit, then I used some metal polish to produce a mirror finish (then used a load of white spirit afterwards to remove any traces of the polish).

Now I don't really bother unless the heatsink looks particularly warped etc.

I was reading a post at xtreme systems where a guy had tried different grade finishes and found to his suprise that he got the lowest temps using 800grit.

He went on to surmise that maybe the more shiny/polished finishes were actually reflecting the heat rather than transfering it? (sorry no link atm to this post).

I think unless you have a really badly produced/or damaged heatsink lapping should be left well alone, until your any good at it, because if done badly (angled) you can make the heatsink worse.

As regards the mirror finish (using polish) I'm still not sure myself, but next time I get the old sandpaper out I will try the 800grit finish to see myself.

[edit] here is my old AERO 7 Lite that I lapped. .

ChrisLX200 · 15 Mar 2006 at 08:45

Big.Wayne said:
[edit] here is my old AERO 7 Lite that I lapped. .

A lovely finish - shame to put heatsink compound on it

I think I see an improvement with my 'lapped' XP120 (job not as carefully done as yours). It's a different processor unfortunately so direct comparison is not possible, but the Opty 170 is giving 29/33 (case/CPU) at idle and 29/35-6 under moderate (75%) load at stock frequency. The fact that there is such a small delta gives me hope the XP120 is now working well and offers opportunity for a good overclock. There was a much larger delta with the 3500+ under similar conditions (~15 delta).