Full system simulators, such as Stanford’s
SimOS, allow computer hardware and software architects to faithfully
model the behavior of today's systems by fully emulating the processor,
memory hierarchy and I/O devices. SimOS supports user-developed packages
for data and instruction cache simulation, the execution profiling
of all code, as well as providing a practical performance and functional
debugging environment for operating systems.
ARL’s Full System Simulation Project has adopted
Stanford’s SimOS to model existing and proposed PowerPC-based machines
in sufficient detail that IBM’s AIX operating system is booted on
SimOS-PPC and, 8 billion emulated instructions later, emits the
login prompt. The emulated system behaves exactly like a real system,
albeit slower. It captures complete traces of both kernel and user
activity.
IBM has used SimOS-PPC as a development environment
for new operating systems such as the K42 project at the Watson
Research Center, and to improve the performance of the speech recognition
software by 17%. It has also used the tool to generate traditional
traces, as well as a framework to plug in detailed models of proposed
processors and memory systems. Additionally, several universities
use SimOS-PPC for architectural and operating systems research.
The success of this project has enabled many
people within IBM to leverage their effort. “We saved at least a
year of development by adopting SimOS-PPC,” Marc Snir, IBM T.J.
Watson Research Center.
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