Bus Interface Unit

Question 1

The BIU consists of a 6-byte long instruction register called Queue.

Answer 1

And four stack segment registers (ES,CS,SS,DS) , one Instruction Pointer(IP) and an adder circuit to calculate the 20bit physical address of a location.

Question 2

This bus interface unit will perform all the external bus operations.

Answer 2

They are fetching the instructions from the memory, read/write data from/into memory or port and also supporting the instruction Queue etc.

Question 3

The BIU fetches up to six instruction bytes from the memory and stores these pre-fetched bytes in a first –in first out register set called Queue.

Answer 3

When the execution unit is ready for the execution of the instruction ,instead of fetching the byte from the memory ,it reads the byte from the Queue .

Question 4

This will increase the overall speed of microprocessor .

Answer 4

Fetching the next instruction while the current instruction executes is called pipelining or parallel processing.

Question 5

Components in BIU

1) segment register
2) The instruction pointer
3) Address generation adder
4) Bus control logic
5) Instruction Queue

Answer 5

Components in EU

1) Arthimetic logic unit, ALU
2) Status and control flags
3) General-purpose registers
4) Temporary-operand registers