> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/dolphin-emu/dolphin/llms.txt
> Use this file to discover all available pages before exploring further.

# IOS emulation

> Wii operating system high-level emulation for system software and hardware interfaces

The Wii runs IOS (Input/Output System), a microkernel-based operating system on the ARM coprocessor (Starlet). Dolphin uses high-level emulation (HLE) to replicate IOS functionality.

## IOS Architecture

IOS consists of a kernel and system modules:

**Location**: `Source/Core/Core/IOS/`

```
IOS/
├── IOS.cpp          # Main IOS kernel
├── ES/              # ES (ETicket Services) - title management
├── FS/              # FS (FileSystem) - NAND filesystem
├── DI/              # DI (Disc Interface) - DVD access
├── USB/             # USB device emulation
├── Network/         # Network services (KD, WD, NCD)
├── SDIO/            # SD card interface
├── STM/             # State Transition Manager (power)
└── Crypto/          # Encryption/decryption
```

## IOS Kernel

**Location**: `IOS/IOS.cpp`

The IOS kernel manages:

* **IPC** (Inter-Process Communication): PowerPC ↔ ARM communication
* **Module Loading**: Start/stop IOS modules
* **Request Handling**: Route IOCTL commands to modules
* **Resource Management**: File descriptors, memory

### IPC Communication

PowerPC communicates with IOS via IPC registers:

```cpp theme={null}
// IPC request structure
struct IPCCommandRequest {
  u32 command;     // Open, Close, Read, Write, Seek, Ioctl, Ioctlv
  u32 fd;          // File descriptor
  u32 arg0, arg1, arg2, arg3, arg4;
};
```

Commands:

* `IPC_OPEN`: Open device (`/dev/es`, `/dev/fs`, etc.)
* `IPC_CLOSE`: Close file descriptor
* `IPC_READ/WRITE`: Read/write data
* `IPC_IOCTL`: Issue control command
* `IPC_IOCTLV`: Vector IOCTL (multiple buffers)

## ES Module (ETicket Services)

**Location**: `IOS/ES/`

Manages Wii titles, tickets, and content:

### Responsibilities

* Title installation and launching
* Ticket and TMD (Title Metadata) verification
* Content decryption (using title keys)
* DLC and update management
* NAND permissions

### Key Functions

```cpp theme={null}
// Launch title
IOCTL_ES_LAUNCH(u64 title_id);  

// Get title info
IOCTL_ES_GETTITLEID(u64* title_id);
IOCTL_ES_GETTITLECONTENTS(u64 title_id, ...);

// Ticket operations
IOCTL_ES_GETTICKETVIEWS(u64 title_id, ...);
IOCTL_ES_ADDTICKET(const u8* ticket);
```

### Title IDs

Wii titles are identified by 64-bit IDs:

```cpp theme={null}
// System titles (high 32 bits = 0x00000001)
0x0000000100000002  // System Menu
0x0000000100000009  // IOS9  
0x000000010000003A  // IOS58

// Game titles (high 32 bits = game code)
0x00010000524D4345  // Mario Kart Wii
```

## FS Module (FileSystem)

**Location**: `IOS/FS/`

Provides NAND filesystem access:

### NAND Structure

```
/
├── sys/           # System files
├── title/         # Installed titles
│   ├── 00000001/  # System titles
│   └── 00010000/  # Game titles
├── shared1/       # Shared save data
├── shared2/       # System data
├── tmp/           # Temporary files
└── meta/          # Metadata
```

### File Operations

```cpp theme={null}
// Open file
fd = IOS_Open("/title/00010000/...", mode);

// Read/write
IOS_Read(fd, buffer, size);
IOS_Write(fd, buffer, size);

// Directory operations  
IOS_ReadDirectory("/title/00010000/", ...);
IOS_CreateDir("/tmp/foo");
```

### FS Backend

**Location**: `IOS/FS/HostBackend/`

Maps NAND filesystem to host directory:

```
User/Wii/
└── title/
    └── 00010000/
        └── 524D4345/  # Title files
            ├── content/
            └── data/   # Save data
```

<Note>
  Dolphin stores the NAND filesystem in `User/Wii/` on the host system. This allows easy backup and inspection of save data.
</Note>

## DI Module (Disc Interface)

**Location**: `IOS/DI/`

Handles DVD access for Wii games:

### Features

* Read disc sectors
* Get disc status and info
* Decrypt partition content
* Handle disc changes

### Disc Partitions

Wii discs have multiple partitions:

* **Update Partition**: System updates
* **Game Partition**: Main game content (encrypted)
* **Channel Partition**: Wii Channels

DI handles decryption using per-partition title keys.

## USB Module

**Location**: `IOS/USB/`

Emulates USB devices:

### USB Subsystems

<Accordion title="Bluetooth (USB/Bluetooth/)">
  Wii Remote communication via Bluetooth:

  * Scan for Wii Remotes
  * Pair and connect remotes
  * HID input reporting
  * Sync button handling
  * Extension detection (Nunchuk, Classic Controller)

  **Emulated Devices**: `/dev/usb/oh1/57e/305`
</Accordion>

<Accordion title="USB HID (USB/USB_HID/)">
  Generic USB HID devices:

  * Keyboards
  * Mice
  * Generic gamepads

  **Emulated Devices**: `/dev/usb/hid`
</Accordion>

<Accordion title="Skylanders Portal (USB/Emulated/)">
  Skylanders portal emulation:

  * Figure detection
  * RFID reading/writing
  * LED control

  **Emulated Devices**: `/dev/usb/lp0`
</Accordion>

<Accordion title="Infinity Base (USB/Emulated/)">
  Disney Infinity base emulation:

  * Figure placement detection
  * NFC communication

  **Emulated Devices**: Custom USB device
</Accordion>

## Network Module

**Location**: `IOS/Network/`

Network services:

### KD (Network/KD/)

NWC24 (Nintendo WiiConnect24) daemon:

* Friend codes
* WiiConnect24 messaging
* Download management

### WD (Network/WD/)

Wifi Driver:

* Wifi configuration
* Access point scanning
* Connection management

### NCD (Network/NCD/)

Network Configuration Daemon:

* Connection settings
* IP configuration (DHCP/static)

### IP Stack (Network/IP/)

TCP/IP implementation:

* Socket API
* TCP/UDP protocols
* DNS resolution

## SDIO Module

**Location**: `IOS/SDIO/`

SD card interface:

```cpp theme={null}
// SD card operations
IOCTL_SDIO_READHCR(...);     // Read SD registers
IOCTL_SDIO_WRITEHCR(...);
IOCTL_SDIO_SENDCMD(...);     # Send SD command
```

Maps to `User/Wii/sd.raw` or host SD card folder.

## STM Module

**Location**: `IOS/STM/`

State Transition Manager:

* Power button handling
* Reset button
* System state transitions
* LED control (slot LED, power LED)

## Crypto Services

**Location**: `IOS/Crypto/`

Encryption and decryption:

### AES Engine

Hardware AES for content decryption:

```cpp theme={null}
// Decrypt title content
AES128_CBC_Decrypt(key, iv, encrypted_data, decrypted_data, size);
```

### Keys

* **Common Key**: Encrypts all Wii content (Dolphin uses dumped key)
* **Title Keys**: Per-title encryption (derived from tickets)
* **SD Key**: SD card content encryption

## IOS Versions

Multiple IOS versions exist:

| IOS   | Purpose                       |
| ----- | ----------------------------- |
| IOS9  | Early system menu             |
| IOS21 | System menu 3.0               |
| IOS36 | System menu 3.2               |
| IOS53 | System menu 4.0               |
| IOS58 | System menu 4.3 (most common) |
| IOS80 | System menu 4.3K (Korea)      |

Games specify required IOS in TMD.

<Note>
  Dolphin HLE emulates all IOS versions with a unified implementation. The IOS version number mainly affects title permissions and available system calls.
</Note>

## Save Data

Game saves stored in NAND:

```
/title/00010000/GAMEID/data/
└── wii_save.bin  # Game save file
```

Dolphin location:

```
User/Wii/title/00010000/GAMEID/data/
```

### WiiSave Format

**Location**: `Core/HW/WiiSave.cpp`

Save files are encrypted:

* AES-CBC encryption with SD key
* SHA-1 HMAC for integrity
* Banner image (96x32 RGB5A3)

## See Also

* [Core Emulation](/architecture/core-emulation)
* [Disc I/O](/architecture/disc-io)
* [Wii Configuration](/user-guide/configuration)