SimOS is the world's fastest and most powerful computer system
simulator, quickly executing commercial operating systems and
applications. As such, it is an excellent platform for operating
system development, architectural evaluation, and application
performance debugging.  SimOS's greatest strength is that it can
track, classify, and visualize every machine-level event that occurs
during the execution of a workload, including cache misses, disk
accesses, exceptions, and instruction execution. The problem is that,
without classification and processing, there is simply too much data
at too low of a level to be useful. We found Tcl to be the ideal
solution to this problem!

Using Tcl, we encourage users to customize their event classification,
mapping these low-level events back to application-level
constructs. Using Tk, the resulting information is presented
graphically throughout the execution of the simulation, providing
immmediate feedback to the user. Tcl was simple to incorporate into
our existing code base, provides a flexible interface for simulator
control, and is fast enough for the real-time processing of our
voluminous data.