This is an unofficial read-only mirror of the gem5 simulator. The upstream repository is stored in Mercurial at with an official git mirror at The mirror is updated at least hourly. Please consider contributing your changes to the upstream project.
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This is the gem5 simulator.

The main website can be found at

A good starting point is, and for
more information about building the simulator and getting started
please see and

To build gem5, you will need the following software: g++ or clang,
Python (gem5 links in the Python interpreter), SCons, SWIG, zlib, m4,
and lastly protobuf if you want trace capture and playback
support. Please see for more details
concerning the minimum versions of the aforementioned tools.

Once you have all dependencies resolved, type 'scons
build/<ARCH>/gem5.opt' where ARCH is one of ALPHA, ARM, NULL, MIPS,
POWER, SPARC, or X86. This will build an optimized version of the gem5
binary (gem5.opt) for the the specified architecture. See for more details and options.

With the simulator built, have a look at for more information on how to use

The basic source release includes these subdirectories:
   - configs: example simulation configuration scripts
   - ext: less-common external packages needed to build gem5
   - src: source code of the gem5 simulator
   - system: source for some optional system software for simulated systems
   - tests: regression tests
   - util: useful utility programs and files

To run full-system simulations, you will need compiled system firmware
(console and PALcode for Alpha), kernel binaries and one or more disk
images. Please see the gem5 download page for these items at

If you have questions, please send mail to

Enjoy using gem5 and please share your modifications and extensions.