Alan Browne wrote:

I'm running 3.08 under WinXP on a Celeron at 2.4 GHz.  I may upgrade to 
a Pentium IV by simply replacing the chip.

You'll have to check that your motherboard and BIOS is compatible with
both chips as they have different pin counts.

Requesting clarification.  When SETI runs a unit, it completes the first 
10% of the unit very quickly (about 1 hour in my case).  After that 
first 10% or so, however, the rate of processing falls to about 3% / 
hour.  Is there some reason for this?

Are you sure it's dropping to only 3%/hr?

How long does it take to process a work unit on average over at least 10
work units?

Are you using the GUI screensaver or CLI command line version?

Can anyone guestimate my performance improvement if I replace the 
Celeron with a Pentium IV at the same clock speed?

Less than you'd think probably.

My P4-2.0GHz processes work units at an average rate of 3.5 hours each
and averaging 28% per hour, according to SetiWatch over the last 60 work
units.

I'm running the command line version 3.08 in low priority mode all the
time, with SetiDriver for caching of work units.