panic on sparc64 running 10-beta4

I installed a sparc V120 (4GB memory, dual 72GB disks) with the 10-beta4
install image today.

Installation went fine.  I rebooted the machine, and then went to get
a fresh ports tree, and the machine panic'd:

root_at_host:/usr/ports # portsnap fetch
Looking up portsnap.FreeBSD.org mirrors... 7 mirrors found.
Fetching public key from your-org.portsnap.freebsd.org... done.
Fetching snapshot tag from your-org.portsnap.freebsd.org... done.
Fetching snapshot metadata... done.
Fetching snapshot generated at Tue Dec  3 19:06:18 EST 2013:
43b6803c6d94efd5b2e2bc9df0b66a84b75417fa3c1728100% of   69 MB 3225 kBps 
00m22s
Extracting snapshot... done.
Verifying snapshot integrity... panic: trap: illegal instruction (kernel)
cpuid = 0
KDB: stack backtrace:
#0 0xc08836d4 at trap+0x554
Uptime: 6m59s
Dumping 4096 MB (4 chunks)
   chunk at 0: 1073741824 bytes ... ok
   chunk at 0x40000000: 1073741824 bytes ... ok
   chunk at 0x80000000: 1073741824 bytes ... ok
   chunk at 0xc0000000: 1073741824 bytes ... ok

Dump complete
Automatic reboot in 15 seconds - press a key on the console to abort
Rebooting...

And then it panic'd again when attempting to run 'savecore'!
(I typed a <ctrl-t> after it printed out the line about
writing the core file, that's where the "load: 0.72 ..." line
came from...)

savecore: reboot after panic: trap: illegal instruction (kernel)
Dec  4 10:49:45 host savecore: reboot after panic: trap: illegal 
instruction (kernel)
savecore: writing core to /var/crash/vmcore.0
load: 0.72  cmd: savecore 906 [physrd] 13.66r 2.75u 2.31s 27% 3192k
vmcore.0 6.5%
panic: trap: fast data access mmu miss (kernel)
cpuid = 0
KDB: stack backtrace:
#0 0xc08836d4 at trap+0x554
Uptime: 1m58s
Dumping 4096 MB (4 chunks)
   chunk at 0: 1073741824 bytes ... ok
   chunk at 0x40000000: 1073741824 bytes ... ok
   chunk at 0x80000000: 1073741824 bytes ... ok
   chunk at 0xc0000000: 1073741824 bytes ... ok

Dump complete
Automatic reboot in 15 seconds - press a key on the console to abort
Rebooting...

Something's rotten with the 10-beta4 binaries for sparc64.

-Kurt