well there are many tips in the SETI readme that accompanies the downloaded client...
mainly, always run as a screensaver and set it to go to blank screen after one minute (in prefs settings), and you can try to overclock your L2 cache using software solutions made to do this... XLR8's Mach Speed Control is the best, imo
SETI likes to have a 1M L2 cache and your iMac has a 512k L2 so that will keep your times somewhat slower than you might like them to be
and of course, search this forum for more tips as they have been repeatedly posted... also see:
http://www.flex.com/~daniel/SETI/
and poke around the SETI homepage for other links to related websites:
http://setiathome.ssl.berkeley.edu/
[This message has been edited by wlonh (edited 09-22-2000).]