Internal structure, Functional parts | 8086 CPU?

 

Internal Structure of 8086 CPU:

Introduction:

The 8086 CPU has internally two main blocks. The Bus Interface Unit (BIU) and the Execution Unit (EU). Where the Bus Interface Unit (BIU) has to perform the function of fetching instructions and data by interacting with the memory and the Input/ Output devices and that data is required by the Execution Unit (EU) of the CPU.

While the Execution Unit (EU) executes instructions from the instruction system byte queue.

Motivation: is yet another internal operation of the 8086 CPU which is mainly a separation system to increase the processing speed of the processor. This separation is actually the separation of the respective functions of the Bus Interface Unit (BIU) and the Execution Unit (EU).

Here is the description of the Bus Interface Unit (BIU) and the Execution Unit (EU) respectively:

Bus Interface Unit BIU):

The Bus Interface Unit (BIU) deals with sending the address on the address bus and sends and receives data via a data bus. It does not only performs the bus operations but also deals with several other operations and functions concerned with instruction and data acquisition. The major and main function of BIU is instruction queuing and address generation. To deal with these functions, the BIU has further connected devices inside like, segment registers, the instruction pointer, the address generation adder, bus control logic, and an instruction queue.

Furthermore, the BIU contains the instruction stream byte queue, a set of segment registers and the instruction pointer.

Execution Unit (EU):

The Execution Unit (EU) executes the instructions. And the microprocessor can fetch other instructions while the execution of instructions by the Execution Unit (EU). This functioning helps to increase the overall speed of the fetch and execute the operation of the microprocessor.

Thus you can conclude that the Execution Unit (EU) decodes instructions fetched by the Bus Interface Unit (BIU), generates and controls signals, and executes all the instructions on the memory fetched by the BIU.

The EU has the following interconnected devices inside to execute the instructions:

The control unit, Instruction decoder, ALU (arithmetic logic unit), general registers, flag registers, pointers, and index registers.