Starting back at instruction 0x0623, we show a 00 byte at Memory location 0x0 7BE: The code just put 07be into the Base Pointer ( BP) Register to checkįor 80h at the correct offset in the first Partition Table entry:ĪX=0000 BX=0000 CX=0004 DX=0000 SP=7C00 BP= 07BE SI=7E00 DI=0800ĭS=0000 ES=0000 SS=0000 CS=0000 IP= 0623 of df IF sf ZF af PF cfĠ623 807E0000 CMP BYTE PTR ,00 SS:07BE=00 To Interrupt 18h (often labeled as "ROM BASIC" since the original IBM® PC's XT and AT models contained the BASIC Programming Language in ROMĬhips). When each of the four 16-byte Partition Table entries (there can only be 4 entries under the standard 'Basicĭisk'/MBR Partitioning Scheme) has only zero ( 00 hex) as its first byte that is, no Active partition is found, the PC's BIOS will automatically jump If you need any help in setting up the Bochs Debugger, pleaseīack to: Pathways through the Windows 7 MBR page.
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