1.1.1 - structure and function of the processor Flashcards
1
control unit (CU)
- Controls and coordinates activities of CPU.
- Directs flow of data between CPU and other devices.
- Decodes instructions.
bus
A set of parallel wires connecting two or more components of a computer.
address bus
- Sends address of data from CPU to memory.
- Unidirectional
data bus
- Moves data between main memory and CPU.
- Bidirectional
control bus
- Sends control signals.
- Bidirectional
arithmetic logic unit (ALU)
Performs arithmetic and logical operations on data.
registers
Small, special memory cells that operate at very high speed. Very specific roles.
program counter (PC)
Holds the address of the next instruction to be executed.
current instruction register (CIR)
Holds the current instruction being executed.
memory address register (MAR)
Holds the address of the memory location from which data is to be fetched or written to.
memory data/buffer register (MDR)
Temporarily stores the data read from or written to memory.
Name the 2 parts of an instruction.
- opcode
- operand
stages of fetch stage
1- Address of next instruction copied from PC to the MAR.
2- Instruction held at that address is copied to MDR.
3- PC is incremented.
4- contents of MDR copied into CIR.
stages of decode phase
- Instruction in CIR is decoded.
- Opcode determines types of instruction and hardware
- Operand hold address of data or the actual data.
stages of execute stage
- Appropriate instruction/opcode is carried out on the operand.
Name 3 factors affecting processor performance.
- clock speed
- number of cores
- amount and type of cache
How does clock speed affect processor performance?
The greater
the clock speed, the faster instructions will be executed.
How does the number of cores affect processor performance?
Each core is theoretically able to process a different instruction at the same time with its own
fetch-execute cycle. However, the software may not always be able to take full advantage of multiple processors.
How does amount and type of cache affect processor performance?
Since cache is inside the CPU, fetching data from cache is much quicker than fetching it from main memory.
pipelining
Without pipelining, the steps in the Fetch-Execute cycle take place one after the other. Using pipelining, the computer architecture allows the next instructions to be fetched at the same time as the processor is performing arithmetic or logic operations, holding them in a buffer close to the processor until the instruction can be performed
Name the 2 pipelines.
1- instruction pipeline
2- arithmetic pipeline
instruction pipeline
Consists of the stages in which an instruction is moved through the processor, including its being fetched, buffered and then executed.
arithmetic pipeline
Represents the parts of an arithmetic operation that can be broken down and overlapped as they are performed.
Explain why pipelining can improve the performance of the processor. [2]
- reduces latency
- an instruction can be fetched while another is decoded
- all parts of the processor can be used at any instance in time.
