The Wii U has a standard AHCI 1.2 SATA controller onboard. It identifies as having two ports (0 and 1) running at 3Gbps. In retail systems, the disc drive is connected to port 0; while port 1 is disconnected. Unused code in IOS-BSP indicates that port 7 may be present on non-retail units.
In terms of hardware registers; the controller lines up with the specification starting at address 0x0D160400; that is; the first Generic Host Control register (Host Capabilities) resides at 0x0D160400. On a retail console, this register reads out 0x7720FF81.
- The generic host control registers start at 0x0D160400.
- The port registers start at 0x0D160500.
Besides commands defined in the ATAPI specification, the Wii U also seems to have some custom commands.
0xDA - ATAPI_DI_READ_DISC_INFORMATION_CMD
0xE0 - ATAPI_DI_REQUEST_ERROR_ID_CMD
0xED - ATAPI_DI_READ_CBC_CMD
0xF0 - ATAPI_CF_REQUEST_DRIVE_ID_CMD
0xF1 - ATAPI_CF_AUTHENTICATE_CMD
0xF2 - ATAPI_CF_START_STOP_UNIT_CMD
0xF3 - ATAPI_CF_READ_CMD
0xF4 - ATAPI_CF_TEST_UNIT_READY_CMD
0xF5 - ATAPI_CF_INQUIRY_CMD
0xFB - ATAPI_CF_FREC_READ_CMD