booting from the openbsd 5.3 i386 cdrom on parallels desktop for mac results in a kernel panic Parallels Build 7.0.14924
openbsd 5.2, 5.1, 5.0, 4.8, 4.5 and their respective current cvs heads still work. (i use those daily) arguably i cant compile my update to cvs current 5.3 this way at the moment (lack of other hardware), so this is untested.
