2. SEGA Partition Structure
Games on the Ring* series use MBR partitioned drives. The core partition structure is as follows:
| Partition | Size | Format |
|---|---|---|
| 1 | 1.5GiB | NTFS |
| 2 | 1.5GiB | NTFS |
| 3 | remaining space | Extended Partition (LBA) |
| 4 |
Extended partitions are structed by a linked list of partition headers at the beginning of each partition. These headers reserve 3Fh blocks for their information, however only use a single block at the start of this for actual data. SEGA make use of the remaining blocks in the first extended partition header for SEGA boot records.
| Partition offset (blocks) | Content |
|---|---|
| 0 | Extended partition header |
| 1 | SEGA Partition Description |
| 2 | SEGA Boot Record (1) |
| 3 | SEGA Boot Record (2) |
| 4-63 | Additional data storage |
| 64-… | Actual partition data |
Two identical copies of the SEGA Boot Record are present. This is for redundancy; if either is corrupted, an attempt will be made to restore it from the other copy.
2.1 SEGA Partition Description
The SEGA Partition Description (SPD) largely echos the structure laid out by the extended partition headers, however is the table SEGA loaders preferentially read. It takes up all 512 bytes of the block; it’s structure is as follows:
The slot content types are:
| Value | Meaning |
|---|---|
| 10h | original0 |
| 11h | original1 |
| 20h | patch0 |
| 21h | patch1 |
| 30h | os |
| 40h | app_data |
2.2 SEGA Boot Record
The SEGA Boot Record (SBR) contains detailed information about the content of each slot.