Boot Descriptor format
| BP | 大きさ | 型 | 名称 | 内容 |
| 0 | 1 | unsigned char | Structure Type | =0 |
| 1〜5 | 5 | char[5] | Standard Identifier | ="BOOT2" |
| 6 | 1 | unsigned char | Structure Version | =1 |
| 7 | 1 | unsigned char | Reserved | =0 |
| 8〜39 | 32 | regid | Architecture Type | 形式 |
| 40〜71 | 32 | regid | Boot Identifier | 起動ID |
| 72〜75 | 4 | unsigned long | Boot Extent Location | 起動情報のアドレス |
| 76〜79 | 4 | unsigned long | Boot Extent Length | 起動情報の大きさ[bytes] |
| 80〜87 | 8 | unsigned int64 | Load Address | ブート情報をコピーするメモリアドレス |
| 88〜95 | 8 | unsigned int64 | Start Address | 制御を開始するメモリアドレス |
| 96〜107 | 12 | timestamp | Descriptor Creation Date and Time | 記録日時 |
| 108〜109 | 2 | unsigned short | Flags | フラグ bit 0 : 0なら有効 1なら無効 |
| 110〜142 | 32 | unsigned char[32] | Reserved | =0 |
| 142〜2047 | 1906 | unsigned char[1906] | Boot Use | 予約 |

