GSSquared is a complete emulator for the Apple II series of computers.

GSSquared has three primary design goals: support both 8- and 16-bit Apple IIs; be cross-platform; have a simple, intuitive user interface and be packaged 100% ready to go.

To my knowledge, it is the only emulator besides MAME that models (most of) the 8-bit Apple II as well as the 16-bit Apple IIgs:

• Apple ][
• Apple ][+
• Apple //e
• Apple //e Enhanced
• Apple //e Enhanced with 65816 CPU
• Apple IIgs

It is written in C++ and runs on:

• Windows
• Linux
• macOS

It has an intuitive user interface and is 100% ready to run without any other downloads.

I think these characteristics make GSSquared unique among Apple II emulators.

It uses the SDL3 library for graphics, sound, and I/O. This is a video game-oriented library and suits an emulator well. It's what made building across three (very different) platforms work.

Check out the User Documentation for detailed instructions on how to use GSSquared.

A binary release is available at https://github.com/jawaidbazyar2/gssquared/releases.

For the Mac, after downloading you will need to tell MacOS the software is A-OK even though it's from the Internet.

% xattr -d com.apple.quarantine gssquared.dmg 

or

xattr -d com.apple.quarantine /Applications/gssquared.app

The code base builds and has been tested on:

• MacBook Pro M1
• Mac Intel
• Mac Mini M4
• Ubuntu Linux 22.04 (x64 AMD)

General Build Instructions:

To build GSSquared, you will need the following:

• clang C compiler or GCC
• SDL3 downloaded and built from the SDL web site. (Specific steps for this are below.)
• git

I use vscode as my IDE, but, this isn't required to build.

Note that GSSquared tries to force-select Clang as the compiler. If you want to override that you can edit the top of the CMakeLists and remove the clang-selection logic.

NOTE: the build process has been updated so that builds are done in and to the build/ directory, as opposed to prior versions of GS2 where builds were done into the project root directory.

GSSquared should also build with GCC on Ubuntu 22.04 or later, but this hasn't been tested.

Production builds are optimized for performance.

cmake -DCMAKE_BUILD_TYPE=Release -S . -B build

Debug enables a variety of assertions, turns off optimizations, and enables memory leak and buffer overrun checking.

cmake -DCMAKE_BUILD_TYPE=Debug -S . -B build

GSSquared will build on both Intel and Apple Silicon Macs.

You will need:

• Mac OSX 12 SDK, either Command-line or full Xcode.

git clone --recurse-submodules https://github.com/jawaidbazyar2/gssquared.git
cd gssquared

If you just want to do a standard build that will result in a Mac App Bundle,

cmake -DGS2_PROGRAM_FILES=OFF  -DCMAKE_BUILD_TYPE=Release -S . -B build
cmake --build build
cmake --install build

This will "install" an App Bundle into the build/ directory, named GSSquared.app. (Or in Finder, just GSSquared)

To go further and build a Mac Disk Image (.dmg file), do this from project root after doing the above build,

cmake --build build --target package

The app bundle and .dmg file are built into the packages/ directory.

PROGRAM FILES Mode will just build executable into build/ (named GSSquared) suitable for execution from the command-line.

cmake -DGS2_PROGRAM_FILES=ON  -DCMAKE_BUILD_TYPE=Release -S . -B build
cmake --build build
build/GSSquared

You may also use -DCMAKE_BUILD_TYPE=Debug , which will disable optimizations, and include debugger symbols in the result.

By default, GSSquared builds as a "Fat Binary" or Dual-Architecture binary for both Apple Silicon and Intel CPUs.

If for some reason you want to build only for your native architecture:

cmake -DBUILD_NATIVE=ON  -DCMAKE_BUILD_TYPE=Release -S . -B build

gs2 Linux build has been tested on:

• Ubuntu 22.04
• clang 14

You need the following libraries installed:

• libasound2-dev
• libpulse-dev
• libudev-dev
• libimgui-dev

git clone --recurse-submodules https://github.com/jawaidbazyar2/gssquared.git
cd gssquared

Then to build:

cmake -DCMAKE_BUILD_TYPE=Release -S . -B build
cmake --build build

Alternatively, build in the "GNU install directories" style:

cmake -DCMAKE_BUILD_TYPE=Release -DGS2_PROGRAM_FILES=OFF -S . -B build
cmake --build build
cmake --install build

Now you should be able to run gs2 at command line anywhere via a GSSquared command, and it should also be available as an application from your applications list.

After building, you can create a folder that contains a complete package for Linux:

cmake --build build --target package

Creates a .TGZ package in the build/ directory that contains all the pieces you need.

We've successfully built for windows using the following environment:

• git bash
• mingw
• clang
• VS Code

git clone --recurse-submodules https://github.com/jawaidbazyar2/gssquared.git
cd gssquared
mkdir build
cmake -G "MinGW Makefiles" -DGS2_PROGRAM_FILES=ON -DCMAKE_BUILD_TYPE=Release -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -B build -S .
cmake --build build --parallel

After building, you can create a ZIP archive for distribution for Windows.

cmake -G "MinGW Makefiles" -DGS2_PROGRAM_FILES=OFF -DCMAKE_BUILD_TYPE=Release -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -B build -S .
cmake --build build --parallel --target package

If you build from source, you will also get a couple of other programs:

Analyzes a disk image and prints information about it.

Convert a disk image file (140K 5.25 .do, .po, .dsk) to nibblized format (e.g. .nib). For testing.

I took the concept of the DisplayNG code from OpenEmulator, under GPL 3. https://github.com/openemulator/openemulator/blob/master/AUTHORS

I also shamelessly copied the Disk II sound files from OpenEmulator.

for the lookup table approach to the new DisplayNG code.

for cycle-accurate video!

for helping test in different build environments, and providing MacOS-Intel builds.

All the amazing people in the SDL Discord, especially Sam!