Adding 32-bit processing

Converting from 16-bit processing to 32-bit processing required the following additions to Sim286: (1) 64 new addressing forms, (2) the addition of SIB byte to the instruction format, (3) adding additional instructions, (4) modifying current instructions to perform 32-bit calculations, (5) modifying segmentation, and (6) increasing the size of the bus and registers. These modifications are described in the sections that follow.

  

Figure: General Instruction Format. This format consists of one or two opcode bytes, a MOD byte, a SIB byte, an address displacement (optional), and immediate data (optional). Prefix bytes can also precede the instruction in order to override the default segment, operand, and address size used. The prefix bytes are optional.