The full range of systems support UltraSPARC I (one) chips should include a comment that Solaris 10 is support only at CPU speeds higher than 200MHz. This info is buried in the release notes and took me 15-20 minutes to find, knowing what I was looking for. See "SPARC: 32-bit Sun4U Kernel" in http://docs.sun.com/app/docs/doc/817-0552/eos-36?l=en&a=view for validation. The products to note this on include Ultra 1, Ultra 2, Enterprise 3000, 4000, 5000, and 6000?, and maybe the Ex500 follow ons. Thanks Steffen