Success! I've managed to boot Solaris 2.5.1/sparc under qemu! It takes long. I started it on my machine (E8200@2.66GHz) yesterday at 18:31, and today at 03:24, I finally got the "#":
WARNING: clock gained 4900 days -- CHECK AND RESET THE DATE!
a devices kernel opt root.proto var
bin etc kvm platform sbin
cdrom export lib proc tmp
dev home mnt reconfigure usr
# uname -a
SunOS 5.5.1 Generic sun4m sparc SUNW,SPARCstation-20
Woo-hoo! Currently I can boot it in a single user mode only, as in normal mode it fails on non-existing SX framebuffer.
Does anyone know how to change module "exclude" list from the adb session?
P.S. 4900 days - didn't notice first, that the date was so special. Hope to boot Solaris 9 earlier than 4900 days after its release date. :)