Apple arm64 and x86 emulation

Apple Silicon + emulation.md

Working with Apple arm64 architecture

For most applications, native vs. emulated modes do not need to be user-managed. However, for development purposes, managing the entire stack's architecture may become necessary.

Emulated terminal environment

For an x86 (Rosetta-emulated) environment, create an emulated Terminal.app:

1. Open Finder
2. Hit cmd + shift + U to open the Utilities folder
3. Right-click + Duplicate Terminal.app
4. Right-click + Rename the duplicate to something obvious - 'RosettaTerm'
5. Right-click + Get Info on the duplicate and check the box for Open Using Rosetta

Architecture of installed software must be fully consistent across the entirety of the stack. You cannot mix e.g. arm64 homebrew packages with x86 Python packages.

Use this emulated terminal for all tasks associated with an emulated architecture.

Homebrew

Homebrew can be installed in parallel on Apple Silicon macs.

The arm64 package will be installed in /opt/homebrew/ The x86_64/i386 package will be installed in /usr/local/ (install with the emulated Terminal) Reference

It appears that homebrew is smart enough to autodetect architecture and adjust HOMEBREW_PREFIX accordingly 👍

We can set the zsh environment to auto-detect architecture by adding the following to .zshrc

archcheck () {
   if [ "$(uname -p)" = "i386" ]; then
     echo "Running in i386 mode (Rosetta)"
     eval "$(/usr/local/homebrew/bin/brew shellenv)"
     alias brew='/usr/local/homebrew/bin/brew'  # not sure aliases will set from within a function
   elif
     echo "Running in ARM mode (M1)"
     eval "$(/opt/homebrew/bin/brew shellenv)"
     alias brew='/opt/homebrew/bin/brew'  # not sure aliases will set from within a function
   else
     echo "Unknown architecture detected: $(uname -p) // $(arch)"
   fi
}
alias native="arch -arm64 zsh && archcheck"
alias rosetta="arch -x86_64 zsh && archcheck"

Alternatively, using the arch command, we can specify the architecture under which to run a single process:

/usr/bin/arch -x86_64 /path/to/exe     # 64-bit x86
/usr/bin/arch -arm64 /path/to/exe      # arm64

Reference

Homebrew

brew () { if [ "$(uname -p)" = "i386" ]; then # echo "Running in i386 mode (Rosetta)" eval "$(/usr/local/homebrew/bin/brew shellenv)" arch -x86_64 /usr/local/homebrew/bin/brew "$@" elif # echo "Running in ARM mode (M1)" eval "$(/opt/homebrew/bin/brew shellenv)" arch -arm64 /opt/homebrew/bin/brew "$@" else echo "Unknown architecture detected: $(uname -p) // $(arch)" fi }

Anaconda

mambaforge has support for native arm64 architecture and comes with mamba preinstalled

Conda envs can be restricted to specific architectures:

Create an environment with a specific architecture requirement:

env_name="changeme"
# set arch for new environment
CONDA_SUBDIR=osx-arm64 conda create -n "$env_name"
# ensure subsequent installs respect arch
conda env --name "$env_name" config vars set CONDA_SUBDIR=osx-arm64
unset env_name

# conda activate <env_name>
# conda install -n <env_name> ...