Thanks for all of the suggestions -- I turned out to have two
problems:

* The BIOS didn't recognize the 512KB cache module.  I had to upgrade
  the BIOS from 1.00.03CL to 1.00.06CL;  Intel provides a utility
  and the BIOS code on thier web site:
  
  ftp://ftp.intel.com/pub/bios/10006CL0.EXE

  They have some more info on the Atlantis at:

  http://www-cs.intel.com/oem_developer/motherbd/as_index.htm

* It appears that the cache was too slow.  When I run the CPU at
  150 MHz (rather than 166MHz) I have no problems.  Hopefully
  this'll all work perfectly at the faster speed once I have
  some 7ns cache.

Thanks again!

Kevin

kml@nas.nasa.gov http://www.nas.nasa.gov/~kml