AT&T 6386 16 Mhz Speedup

[Bob DeBula]

Last fall, I obtained an AT&T 6386 16 Mhz machine at a real reasonable (then)
price.  While I was installing my ESDI drive, I took time out to examine
the upside-down motherboard.  One peculiarity struck me immediately: the
386 chip is marked 20Mhz!!! Apparently AT&T (Olivetti) must have decided 
to standardize production.  I also located the 32.000 Mhz clock chip (I
think).  Now the intriguing question is; Can I replace the clock chip (which
appears to be soldered and I have no idea where to obtain the 40.000 Mhz
equivalent) and get a 20 Mhz machine?  My orignial memory which came with the
machine was 80ns (overkill I think).  I purchased 4 1Mb SIMMs from a chip
peddler and installed them (and removed the 256K SIMMs which I promptly
stuck in my MAC-II to make it a 2Mb machine). These SIMMs are 100ns (the
chip peddler insisted that they work fine in a 20Mhz 6386).  In any case,
has anyone else noticed this (or done anything about it)?  I think I'll
hold off while the warranty lasts, but it seems awfully tempting to get
a 20% or so increase in speed by replacing a clock crystal :-).  Is there
something I'm not thinking of (i.e. did Olivetti/AT&T put something in there
to stop hardware hacks such as this?)?  Thanks for any help you may give.