PPSSPP is a PSP emulator written in C++. It translates PSP CPU instructions directly into optimized x86, x64, ARM or ARM64 machine code, using JIT recompilers (dynarecs).
PPSSPP can thus run on quite low-spec hardware, including stronger ARM-based phones and tablets, as long as there's OpenGL ES 2.0 support.
PPSSPP is an open source project, licensed under the GPL 2.0 (or later). Anyone is welcome to contribute their improvements to the code. The code is hosted at the Github page for PPSSPP, using the Git source control system.
Following the Dolphin tradition, the PPSSPP project is very open. Anyone can participate directly in the development by making pull requests, and if you make substantial contributions you may be given rights to commit directly.
You'll find yourself relying on the logs a lot to figure out what's really going on. As PPSSPP simulates the PSP OS, we get something similar to a Unix-style strace.
There's a headless (no display/audio) build, which is very useful when running the pspautotests through test.py - highly recommended way to find issues.
The Windows port and the Qt build have interactive debuggers (Qt currently broken). This is not available for mobile platforms and "SDL" builds.
PPSSPP is a HLE ("high level emulation") emulator, it simulates the PSP OS as seen by the game rather than the full hardware. A program running on the PSP OS can send raw display lists to the graphics chips, but can't access the flash controller or the Media Engine directly, instead it has to go through libraries and the PSP OS kernel. We simply simulate these. This is a lot of work though, the PSP OS is large and has plenty of functionality so achieving 100% compatibility is difficult bordering on the impossible. We can get close though.
Since this emulator implements most of the PSP OS in order to run games, testing it against the real thing is critical. Some other PSP emulator authors have collaborated around creating a test suite called pspautotest, and we have picked that up and expanded it. There are two scripts: test.py and gentest.py. gentest.py uses psplink to run a test program on your real PSP and captures the text output and saves it as [test].expected. Then you can run the same test in PPSSPP by using test.py, which will automatically compare the output to the expected output.
Pick from the list of tasks below, go look at the open issues on GitHub, or just implement whatever missing feature you feel like. Send your code as a pull request on Github. If you send a couple of good pull requests, you'll be added as a contributor and get your own commit access.
The PPSSPP coding style is similar to the Google C++ coding style.
You are encouraged to port PPSSPP to new platforms. Here's an incomplete list of platforms that PPSSPP could or could not be ported to (last updated February 2018):
|Windows||Done||JIT for x86 and x64|
|Android||Done||JIT for ARM, ARM64, x86, x86-64|
|Linux||Done||JIT for ARM, ARM64, x86, x86-64|
|MacOSX||Done||JIT for x86 and x64. Port still pretty bad.|
|iOS||Done||JIT works. Not allowed in Apple Store.|
|Blackberry 10||Done (no longer maintained)||JIT for ARM|
|Symbian||Done (no longer maintained)||JIT for ARM|
|Pandora||Done (no longer maintained)|
|Raspberry Pi||Done||JIT working|
|Windows UWP/Xbox One/WinPhone10||Partial, unsupported||JIT for x86 and x64|
|Meego||Done||Done (no longer supported)|
|Windows Phone 7.x||NOT POSSIBLE||No native code support|
|Windows Phone 8||NOT POSSIBLE||JIT not allowed, would be way too slow|
|Nintendo Switch||LIKELY POSSIBLE||We'll see.|
|Xbox 360||POSSIBLE||Hacked consoles only. Unlikely to happen.|
|Playstation 3||POSSIBLE||Hacked consoles only. Unlikely to happen.|
|Wii||NOT POSSIBLE||Not enough RAM.|
|Xbox Original||NOT POSSIBLE||Not enough RAM.|
|Playstation 2||NOT POSSIBLE||Lack of RAM, weak CPU.|
|Gamecube||NOT POSSIBLE||Lack of RAM|
|Dreamcast||NOT POSSIBLE||Lack of RAM, weak CPU.|