Bus Interface Unit in 8086 Krish Advani 13/02/2013 Engineering 1 Comentario The 8086 Processor is divided into two parts: Execution Unit and the Bus interface unit. Below are mentioned the features of the Bus Interface Unit and the segment registers inside it. Functions of Bus Interface Unit (BIU) Major function of BIU is to fetch instruction data from memory and write data (result) back to memory. It also reads and writes data from Input/output ports. To perform memory operations it generates 20-bit physical address. Segment Registers and Instruction Pointer To access memory there are five pointers available inside the processor – CS, DS, SS and ES registers and IP. The segment registers points to base location of different memory segments of current program. The Instruction pointer used with CS register for Instruction Sequencing. The CS:IP together specifies address of the current instruction be fetched from memory. Instruction Queue The BIU has 6-byte (first in first out) Instruction Queue used in pipelining. Queue holds instructions to be executed by Execution Unit. Due to Instruction Queue it is possible to pre-fetch the instructions while Execution Unit is decoding or executing previous instructions. Instruction Queue speed up the execution of 8086.