[Simh] Breaking change in vax780 from 3.7.0 to 3.7.1 causes VMS 3.0 to fail

Tim Pinkawa timpinkawa at gmail.com
Sat Dec 8 19:51:52 EST 2007


I noticed a bug in the vax780 simulator that was introduced between
version 3.7.0 and 3.7.1 that still exists in 3.7.3 when booting a VMS
3.0 standalone backup following these instructions:
http://mailman.trailing-edge.com/pipermail/simh/2006-December/000865.html

Working case:

VAX780 simulator V3.7-0
./vax780.ini> SET RX DISABLED
Command not allowed
Overwrite last track? [N]
RP: unit is read only
Overwrite last track? [N]
./vax780.ini> SET RP2 DISABLED
Command not allowed
sim> boot rp1
Loading boot code from vmb.exe


  VAX/VMS Version V3.0 26-APR-1982 16:21


$

---------------------------------

Broken case:

VAX780 simulator V3.7-1
./vax780.ini> SET RX DISABLED
Command not allowed
Overwrite last track? [N]
RP: unit is read only
Overwrite last track? [N]
./vax780.ini> SET RP2 DISABLED
Command not allowed
sim> boot rp1
Loading boot code from vmb.exe


  VAX/VMS Version V3.0 26-APR-1982 16:21



**** FATAL BUG CHECK, VERSION = V3.0 INVEXCEPTN, Exception while above
ASTDEL or on interrupt stack

    CURRENT PROCESS = SWAPPER

    REGISTER DUMP

        R0 = 00000007
        R1 = 04070000
        R2 = 00000000
        R3 = 00000000
        R4 = 80002568
        R5 = 00000000
        R6 = 00000000
        R7 = 00000000
        R8 = 00000000
        R9 = 00000000
        R10= 00000000
        R11= 00000000
        AP = 00000000
        FP = 00000000
        SP = 8014DFD0
        PC = 80003DC6
        PSL= 04070009

    KERNEL/INTERRUPT STACK

        8014DFD8  00000004
        8014DFDC  00000000
        8014DFE0  FFFFFFFD
        8014DFE4  00000000
        8014DFE8  00000000
        8014DFEC  00000001
        8014DFF0  00000003
        8014DFF4  00000454
        8014DFF8  80009ABB
        8014DFFC  04070000

Reboot requested, PC: 800039EC (HALT)


My findings:

3.6.1 - works
3.7.0 - works
3.7.1 - crashes
3.7.2 - crashes
3.7.3 - crashes

I am a mere VMS user, so unfortunately I can't really help with fixing
the bug, but I hope someone smarter than I am can figure it out. :)

Thank you,
Tim



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