gem5: document --abs-max-tick

README.adoc

@@ -12054,6 +12054,10 @@ The exact same can be achieved with the older hardcoded `--maxinsts` mechanism p
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+Other related fs.py options are:
+
+* `--abs-max-tick`: set the maximum number of ticks rather than instructions
+
 The message also shows on <<user-mode-simulation>> deadlocks, for example in link:userland/posix/pthread_deadlock.c[]:
 
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