User manual

VAX MP SIMH console extensions
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Desired recording method is selected by user via VAX MP SIMH console command, for example
SET CPU HISTORY=200/SYNC
selects recording of globally sequenced history, while
SET CPU HISTORY=200/UNSYNC
selects recording of locally sequenced per-CPU histories that are not synchronized across the
processors. Default is SYNC.
Command SHOW CPU HISTORY by default displays recorded history for current default
processor, i.e. one selected by command CPU ID. To display globally sequenced instruction
streams history for all processors, rather than just currently selected processor, use console
command
SHOW CPU HISTORY=SYNC
or
SHOW CPU HISTORY=10/SYNC
to display ten last commands from the whole system-wide history of instruction streams.
Without SYNC option, SHOW CPU HISTORY command applies to currently selected processor’s
instruction stream only.
VAX MP also provides a setting that allows instruction history recording be stopped when
processor executes BUGW or BUGL pseudo-instruction. This is helpful for debugging VMS
system crashes, since recording gets stopped at the point bugcheck was generated, and history
buffer is not flushed by subsequent instructions. To activate this setting, execute SIMH console
command
DEPOSIT BUGCHECK_CTRL 1
Breakpoints
SIMH breakpoint facility had been extended for VAX MP to support multiprocessing.
Multiple nearly-simultaneous breakpoint hits on multiples processors are supported. During
execution of breakpoint actions, CPU context is set to the CPU that hit a particular breakpoint. If
multiple CPUs hit multiple breakpoints almost simultaneously, all triggered breakpoint actions
will be invoked in their appropriate CPU contexts.
The logic for breakpoint handling in multiprocessor case is as follows. Once a breakpoint is
triggered on one or more processors, all processors are stopped and control is transferred to the
console thread. Console thread examines processors for triggered breakpoints and builds in-