> my filesystem crashed when I was experimenting with nfs over
> a ppp-link to my Linux box (I know, one should'nt challenge the daemons..).

How did the system crash?  Did it hang?  Did it panic?

> So I've reinstalled the broken files (about 80% of the /usr directory).
> Though, when I execute "systat" or "top", I get the error:
> 	systat: nlist: can't find following symbol: _ccpu
> and top reports: top: nlist failed.

You might want to check the 

> Might the breakdown of the fs have anything to do with the combination
> of the high load of the cpu with interrupts from the serial port and
> the scsi driver?

It's hard to tell without some more information about the crash.  The
filesystem was corrupted because it was in the middle of updating things
when the system halted.  To increase filesystem performance, a certain
amount of data is cached in the kernel.  If the system crashes before
that data is written to disk, then the filesystem will be somewhat
scrambled.

If you can, when the system panics, please enter the panic message down.
If the system is hung, enter the debugger (either through a programmer's
switch or through the CTRL-PWR or CMD-PWR key combinations).
In either case, from the kernel debugger, enter the command "trace"
and copy the results down.  If the hang appears to be SCSI related (like
if the trace contains ncr5380 functions, or if the hard drive light is
on), also enter "call _pdma_stat" and copy down the output.

Most of the time, I will not be able to reproduce your problems, so the
above info (along with good info on what you were doing--like you gave)
will help me gain some insight into what might be happening.

Thanks,
-allen

-- 
Allen Briggs - end killing - allen.briggs@bev.net ** MacBSD == NetBSD/mac68k **
   Where does all my time go?  <a href="http://www.netbsd.org/">Guess.</a>