The unexpected exception/interrupt through vector 420 problem typically occurs during the O/S boot process and is well documented in real Alpha hardware behavior. The system self corrects by rebooting, as shown in the example below.
ff.fe.fd.fc.fb.fa.f9.f8.f7.f6.f5.
ef.df.ee.ed.ec.f4.eb.ea.e9.e8.e7.e6.....e5.
V7.0-9, built on Mar 18 1999 at 13:25:37
CPU 0 booting
(boot dka200.2.0.6.0 -flags 0)
block 0 of dka200.2.0.6.0 is a valid boot block
reading 1226 blocks from dka200.2.0.6.0
bootstrap code read in
base = 1f2000, image_start = 0, image_bytes = 99400
initializing HWRPB at 2000
initializing page table at 1e4000
initializing machine state
setting affinity to the primary CPU
jumping to bootstrap code
unexpected exception/interrupt through vector 420
process idle, pcb = 001159D0
pc: 00000000 00116A24 ps: 00000000 00001F04
r2: 00000000 001112A0 r5: 00000000 00001F04
r3: 00000000 00022650 r6: 00000000 00001259
r4: 00000000 000EE658 r7: 00000000 0000000A
exception context saved starting at 00116900
GPRs:
0: 00000000 00000000 16: 00000000 00116A08
1: 00000000 000001F4 17: 00000000 00006000
2: 00000000 000ED330 18: 00000000 000384C0
3: 00000000 00076CC0 19: 00000000 0012DD10
4: 00000000 000EE658 20: 00000000 0012DD10
5: 00000000 00038B88 21: 00000000 00000000
6: 00000000 00001259 22: 00000000 00116A08
7: 00000000 0000000A 23: 00000000 00000001
8: 00000000 00110670 24: 00657174 00000000
9: 00000000 00110678 25: 00000000 00000001
10: 00000000 000D0DE8 26: 00000000 00116A20
11: 00000000 00000001 27: 00000000 00111940
12: 00000000 001159D0 28: 00000000 00038BD8
13: 00000000 00000010 29: 00000000 00000000
14: 00000000 00000011 30: 00000000 00116A40
15: 00000000 00000000
dump of active call frames:
breakpoint at PC 1108e0 desired, XDELTA not loaded
ff.fe.fd.fc.fb.fa.f9.f8.f7.f6.f5.
ef.df.ee.ed.ec.f4.eb.ea.e9.e8.e7.e6.....e5.
V7.0-9, built on Mar 18 1999 at 13:25:37
CPU 0 booting
(boot dka200.2.0.6.0 -flags 0)
block 0 of dka200.2.0.6.0 is a valid boot block
reading 1226 blocks from dka200.2.0.6.0
bootstrap code read in
base = 1f2000, image_start = 0, image_bytes = 99400
initializing HWRPB at 2000
initializing page table at 1e4000
initializing machine state
setting affinity to the primary CPU
jumping to bootstrap code
OpenVMS (TM) Alpha Operating System, Version V8.3
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