I downloaded the 1.5T test kernel from ftp.NetBSD.ORG:/pub/NetBSD/arch/sparc64/
and tried booting my Ultra 5+ from it.  It dies with a kernel trap in zsopen():

[...]
root device: sd0a
dump device (default sd0b): sd0b
file system (default generic): ffs
root on sd0a
dump on sd0b
Automatic boot in progress: starting file system checks.
[...]
Setting tty flags.
data fault: pc=1238f8c addr=48 sfsr=800809<ASI=80,ASI,W>
kernel trap 30: data access exception
Stopped in pid 34 (ttyflags) at zsopen+0x4c:	ldx		[%o0 + 0x48, %l1
db> t
spec_open(6,30,10e5818, 19faa00, 8cb4000, 8c8a000) at spec_open+0x1ac
VOP_OPEN(8caf900, 5, 19f9f80, 8c6b3b0, 400, 8008) at VOP_OPEN+0x34
vn_open(0, 5, 8caf900, ffffffffffffd4b0, badcafe, badcafe) at vn_open+0x298
sys_open(0, 8cb7dd0, 8cb7dc0, 10d6bb0, badcafe, badcafe) at sys_open+0x9c
syscall(5, 8cb7e0, 0, 103100, 400, 0) at syscall+0x304
syscall_setup(ffffffffffffd4b0, 4, 0, 10c350, 20e278, 20e340) at syscall_setup+0x140
db> 

Looks like the serial port driver gave it heartburn.

Back to 1.5,

	- Greg