It's been quite long since I last wrote an emulator, and I wanted to get into emulating a classic system.
Well personally, I find C++ to be good while writing emulators. I should probably try rust or zig, but it is what it is.
The emulator is divided into several different subsystems,
-
Graphics and GUI subsystem – The name says it all. I use OpenGL (yes even on Apple systems, it is "good enough" for my use-case) along with GLFW and Dear ImGui.
I have a custom image class to send images to the GPU for drawing. Other than the image class, and the application entrypoint, nothing is coupled to OpenGL, and in theory I can replace it with Vulkan, or even use it platform specific implementations for Metal and DirectX in the future.
-
CPU – The classic MOS 6502 without the decimal mode.
-
Bus - Technically the whole NES system, as everything comes together here. What even is CPU in isolation?
-
PPU – The picture processing unit of the NES.
-
APU (WIP) – Audio processing unit. I haven't implemented this yet.
-
Carts and mappers – The plasic with a PCB inside.
You'll need a couple things installed before you can get going,
- CMake
- Ninja (or
make) - Clang (Can probably use GCC but MSVC won't work for sure)
- vcpkg
- XCode on macOS / Visual Studio with the C++ desktop workload on Windows
You can then build it in release mode using
$ cmake -Bcmake-build-release -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -GNinja -DCMAKE_BUILD_TYPE=Release -DCMAKE_TOOLCHAIN_FILE=[path to vcpkg]/scripts/buildsystems/vcpkg.cmake
$ ninja -Ccmake-build-releaseWell you can build it in debug mode as-well, but keep in mind that it enabled trace
level logging which logs ~50 lines per machine cycle, and the machine runs at 5.3MHz.
You run the risk of logging gigabytes of logs.
Also, it enables address sanitizer which decreases program speed by a factor of two. It is recommended to build in release unless you know what you are doing.