THE CENTRAL PROCESSING UNIT (C.P.U) 1_SS 2NOTES
THE CENTRAL PROCESSING UNIT (C.P.U) 1
Meaning and Components of the CPU - Control Unit (CU) - Arithmetic Logic Unit (ALU) - and Registers
- AC ( accumulator )
- DR ( Data registers )
- MAR ( Address registers )
- PC ( Program counter )
- MDR ( Memory data registers )
- IR ( index registers )
- MBR ( Memory buffer registers )
- Current Instruction Register (CIR)
- AC ( accumulator ) : This is a type of register for short-term, intermediate storage of arithmetic and logic data in a computer's central processing unit (CPU).
- Data registers (DR): is used to hold data that will be stored or fetched from the computer memory, also known as random-access memory (RAM).
- Program counter (PC): is a register in a computer processor that contains the address (location) of the instruction being executed at the current time.
- Memory data registers (MDR): This holds data that is being transferred to or from memory.
- Index Registers (IR): holds the current offset of a memory location, with another register holding the base address, so the combination of the two registers creates a completed memory address.
- Memory buffer registers (MBR) : is the register in a computer's CPU that stores the data being transferred to and from the immediate access storage.
- Current Instruction Register (CIR): This contains the current instruction during processing. It holds the current instruction to be executed.
. No. |
Register |
Main Memory |
|
1. Registers hold operands or instructions that CPU would be currently processing. |
Memory holds instructions and the data about the currently
executing program required by the CPU. |
|
2. They contain small amounts of data− 32bits to 64bits. |
Memory can range from some GB (Giga bytes) to TB (Tera bytes). |
|
3. CPU can operate on the contents of the register at the rate of more than one operation during one clock cycle. |
The CPU accesses memory at a slower rate in comparison to memory
access in a register. |
|
4. There are many types of registers− Accumulator register, Program
counter, Instruction register, Address register. |
There are different types of memory− RAM, ROM. |
|
5. They can be controlled, i.e. information can be stored and retrieved from them. |
The memory can’t be controlled. |
|
6. It is quick in comparison to memory. |
RAM is slow in comparison to registers. |
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