since copper is so much more heat conductive than AS3, i think the claims of poorer performance with a lapped block may be errors caused by poor installation. the main issues i see:
1) rougher surfaces have channels that let the AS3 flow out while it settles, so ppl who goop on AS3 do better with rougher surfaces (supports claims of cooler temps after a "break-in period").
2) excess AS3 reduces the total area of copper in direct contact.
3) theoretically a smoother & flatter surface conducts heat better, but the gap between the HSF & core is so small that the performance is almost entirely dependant on the quality of the installation. i mean, it's easy to add 50 or so microns overall by abusing AS3. it is more difficult to reduce the overall gap the same amount by lapping.
example:
Mr. n00b laps his core to 1600grit, but goops on 2 "BB's" worth of AS3. Mr.n00b has an average 200 microns of AS3 between his core & block.
Mr.modson left his block with a 600grit finish & applies a nice thin film of AS3. thus modson has an average 150mm gap.
n00b spent 1hr extra on lapping, & now knows why his block doesn't work as well as modson.
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