Why do we need instruction buffer in a pipelined CPU?

Design considerations. Pipelining keeps all portions of the processor occupied and increases the amount of useful work the processor can do in a given time. Pipelining typically reduces the processor’s cycle time and increases the throughput of instructions.

What is instruction buffer?

A key part of this architecture is an instruction buffer which both provides storage for prefetched instructions and performs hardware looping. The cycle time for the instruction buffer is around three times slower than the micropipeline FIFO.

What is the role of fetch & decode instruction during execution?

The main job of the CPU is to execute programs using the fetch-decode-execute cycle (also known as the instruction cycle). When a program is being executed, the CPU performs the fetch-decode-execute cycle, which repeats over and over again until reaching the STOP instruction.

Why do we need buffer register?

It acts as a buffer allowing the processor and memory units to act independently without being affected by minor differences in operation. This register holds the contents of the memory which are to be transferred from memory to other components or vice versa.

Which buffer is used in instruction pipeline?

Prefetch Buffers ln one memory-access time, a block of consecutive instructions are fetched into a prefetch buffer as illustrated in Fig. Three types of buffers can be used to match the instruction fetch rate to the pipeline consumption rate.

What is relation between number of stages and speed up?

The maximum speed up that can be achieved is always equal to the number of stages. This is achieved when efficiency becomes 100\%. Practically, efficiency is always less than 100\%. Therefore speed up is always less than number of stages in pipelined architecture.

What is difference between MAR and MBR?

* MAR The Memory Address Register is used to store the address to access memory. * MBR The Memory Buffer Register stores information that is being sent to, or received from, the memory along the bidirectional data bus. If the data is an instruction it gets moved to the Instruction Register.

What is difference between buffer and register?

The main difference between register and buffer is that a register is a temporary storage area in the processor that allows transferring data faster while buffer is a temporary storage area in main memory that holds data before using them.

What is the difference between fetch and decode of instruction?

Fetch : get the instruction from memory into the processor. Decode : internally decode what it has to do (in this case add). Store : store the result back into another register.

What happens in the fetch stage?

During the fetch stage, the address stored in the PC is copied into the memory address register (MAR) and then the PC is incremented in order to “point” to the memory address of the next instruction to be executed.

Which acts as a buffer between the CPU and main memory?

Cache memory is an extremely fast memory type that acts as a buffer between RAM and the CPU.

What is instruction fetch?

The instruction cycle (also known as the fetch–decode–execute cycle, or simply the fetch-execute cycle) is the cycle that the central processing unit (CPU) follows from boot-up until the computer has shut down in order to process instructions.