# ps2xIOP

`ps2xIOP` runs original IRX modules on an R3000A interpreter, with a virtual
IOP kernel providing imports without a PS2 BIOS. The C++20 static library
`ps2_iop` / `ps2x::iop` is linked into `ps2xRuntime`.

## Execution policy

Game-specific IOP code executes from IRX modules. There is no game-profile
selection or native profile-plugin loader. A physical IRX RPC server is
authoritative for its SID.

Generic HLE services remain available when no loaded IRX provides an endpoint:

| Service | SID | Activation |
| --- | --- | --- |
| MCSERV | `0x80000400`, `0x80000480` | Recognized module load |
| LIBSD | `0x80000701` | Recognized module load |
| DBCMAN | `0x80001300` | Recognized module load |

These services are dormant before module load and after reset or the final
module stop. Unknown modules fail to load; unknown RPC SIDs remain unhandled.
Games previously using TSNDDRV, CRI DTX, CLFILE, SOUND or SDRDRV profiles now
require their IRX modules and support for the imports and hardware they use.

## Lifecycle and transport

- `reset()` clears loaded modules, HLE service state and emulator state.
- `loadModule(...)` / `loadModuleBuffer(...)` load and start an IRX.
- `stopModule(...)` releases a module and its owned state.
- `runEeCycles(...)` advances the IOP from EE cycle accounting.
- `selectRpcAbi(...)`, `handleRpc(...)` and `onSifTransfer(...)` connect SIF transport.

IOP RAM is separate from EE RAM. The transport copies data through the IOP
memory accessors; SIF notifications do not mirror bytes into equal-numbered EE
addresses. `RpcResult` describes completion and dispatch actions for the runtime.

Link with `target_link_libraries(my_runtime PRIVATE ps2x::iop)`. The public API
is [iop_subsystem.h](include/ps2x/iop/iop_subsystem.h); `PS2Runtime` owns its
subsystem and host adapter.

## Diagnostics and tests

`debugSnapshot()` exposes emulator cycle/instruction counts, loaded module,
thread and RPC-server counts, generic service metrics and load diagnostics.
The runtime debugger renders these in the **IOP/SIF** tab.

Build standalone tests with:

```sh
cmake -S ps2xIOP -B out/build/iop-tests -DPS2X_IOP_BUILD_TESTS=ON
cmake --build out/build/iop-tests
ctest --test-dir out/build/iop-tests --output-on-failure
```

The suites cover IRX execution, RPC, imports, version resolution and generic
HLE compatibility. `ps2x_tests` also covers runtime SIF RPC/DMA integration.