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This is an read-only mirror of the gem5 simulator. The upstream repository is stored in, code reviews should be submitted to The mirrors are synchronized every 15 minutes.

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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, zlib, m4, and lastly protobuf if you want trace capture and playback support. Please see for more details concerning the minimum versions of these tools.

Once you have all dependencies resolved, type 'scons build//gem5.opt' where CONFIG is one of the options in buildopts like ARM, NULL, MIPS, POWER, SPARC, X86, Garnetstandalone, etc. This will build an optimized version of the gem5 binary (gem5.opt) with the the specified configuration. See for more details and options.

The main source tree includes these subdirectories: - buildopts: pre-made default configurations for gem5 - buildtools: tools used internally by gem5's build process. - configs: example simulation configuration scripts - ext: less-common external packages needed to build gem5 - include: include files for use in other programs - site_scons: modular components of the build system - 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 may need compiled system firmware, kernel binaries and one or more disk images, depending on gem5's configuration and what type of workload you're trying to run. Many of those resources can be downloaded from, and/or from the git repository here:

If you have questions, please send mail to [email protected]

Enjoy using gem5 and please share your modifications and extensions.

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