iec - Instruction Emulator Control
iec p | s [value]
iec p | s [keyword]
The following options are used with the iec command:
p Sets or displays the current option setting for the parent process.
s Sets or displays the current option setting for the system.
The following keywords are used with the p option:
Resets the current option settings to the default settings for the
Does not print the instruction emulation warning message for the parent
Disables instruction emulation. Any programs that attempt to execute
instructions that are not implemented in the host processor will
receive the SIGILL (illegal instruction) signal.
Prints the instruction emulation warning messages for all instances of
instruction emulation. By default, a message is only printed for the
The following keywords are used with the s option:
Resets the current option settings to the default settings for the sys-
Does not print the instruction emulation warning message for the sys-
If value is not specified, the current option setting is displayed. You
can specify value as either 0 (zero) or 1 (one). If value is 0 (zero), the
option is turned on and messages are not displayed. If value is 1 (one),
the option is turned off and messages are displayed.
Keywords can be used singly or in any combination. However, the reset key-
word overrides any other keywords that it is used with.
Usually, the parent process is the shell.
Some processors in the Alpha processor family do not implement all of the
instructions defined in the Alpha architecture. The operating system pro-
vides an instruction emulator that permits all programs written for the
Alpha architecture to run, regardless of the Alpha processor being used.
When the operating system encounters an instruction that is not implemented
by the host processor, the default action is to emulate the instruction and
print a message informing the user process that the emulation has occurred.
By default, the operating system prints a message only for the first
instance of emulation, although it continues to emulate any other non-
implemented instructions that it encounters. The message has the form:
"inst emulated pid=nnn <prog_name> va=0xvirtual_addrpc=0xpc_addr
inst=0xactual_instr". Receiving this message tells you that your applica-
tion will run at less than its optimal level of performance. You may wish
to recompile your program to get better performance. For information on how
to compile for a specific hardware platform, see the compiler manpage for
the language you are using.
In addition, the default action for the operating system is to not deliver
a SIGILL signal to the parent process when an emulated instruction is
These defaults are satisfactory for most users, but some users require a
different behavior and want to specify their own Instruction Emulator Con-
The iec command enables or disables the display of "inst emulated" mes-
sages. The command sets or displays the IEC_NOPRINT, IEC_NOEMUL, and
IEC_VERBOSE flags, as defined in setsysinfo(2).
You must be superuser to set the system option.
1. Both of the following commands disable messages for the parent pro-
# iec p 0
# iec p noprint
2. Both of the following commands enable messages for the system:
# iec s 1
# iec s reset
3. The following command enables the printing of a message for each emu-
# iec p verbose