Difference between Cache Memory and Register

Cache memory and Registers are two types of computer memory components with distinct differences in terms of speed, size, and access time.

Cache memory is a separate unit of memory that stores frequently used data to speed up processing by the CPU. Conversely, registers are high-speed storage devices that hold recent data processed by the CPU.

To speed up processing, the CPU copies recently used data from the primary memory into the cache memory. On the other hand, when the CPU needs to execute an operation on specific data, it saves this data into registers.

Registers are much faster than cache memory due to their compact size and high-speed access. As a result, registers are positioned at the highest level of the memory hierarchy when compared to cache memory.

What is Cache Memory?

Cache memory is a separate memory unit that works with the primary memory. It is significantly smaller and quicker than the main memory. This is due to its close association with the CPU, so it is integrated into the processor chip.

Because it is smaller than the main memory, it cannot hold the complete program simultaneously. As a result, it includes program segments (a collection of instructions) that are now being executed. It stores the data linked to it and the set of instructions.

How does Cache Memory Works?

At first, the program and its related data are in the primary memory when the cache is empty.

When the processor executes the program, it reads the instructions from the primary memory and stores them on the processor chip (registers). It also saves a copy of each instruction in the cache.

If the execution of a specific instruction requires any additional data, the processor retrieves it from the primary memory and copies it to the cache memory.

These instructions must be run repeatedly (as in a loop). If the instructions are in the cache, the processor will access them immediately from the cache memory. Because the cache is quicker than the primary memory which will eventually speed up execution.

Types of Cache Memory

Cache is classified into several levels. We can categorize them based on their size as well as their speed.

• Level 1 Cache: This is the smallest of all caches and is significantly quicker than every other cache.
• Level 2 Cache: The level 2 cache is bigger and slower than the level 1 cache.
• Level 3 Cache: This cache is bigger but slower than the level 1 and 2 caches.

What is Register?

Registers are units of memory incorporated into the CPU chip. It is a computer's smallest memory unit. A register's memory capacity ranges from 2 MB to a few KB. It can only hold one word of data. It also has the shortest access time as it is nearest to the CPU.

Every CPU has registers for storing instructions, temporary results, and variables.

How does Register Works?

A piece of software (program) is a collection of instructions that are loaded into the primary memory for execution. It takes longer to access an instruction from primary memory than it does to execute it. As a result, the CPU employs registers to store instructions, crucial variables, and temporary results.

Throughout program execution, each instruction or a word from the primary memory is transferred into the Register every time. After then, Central Processing Unit reads the instructions from the Register and executes them. The CPU even stores temporary and ultimate results in registers and transfers data from registers to the primary memory.

Types of Registers

1. General Purpose Registers: Also known as processor registers, they perform various roles, including holding operands which are loaded from memory for processing.

2. Memory Buffer Register (MBR): This Register stores a word retrieved from the primary memory or an I/O unit. It even saves the word that the process needs to transmit back to the primary memory or the I/O unit.

3. Memory Address Register (MAR): This Register specifies the memory address by which the word is read into MBR or by which the MBR stores the word in the memory.

4. Instruction Register (IR): This Register stores the presently executed 8-bit opcode (machine instruction).

5. Instruction Buffer Register (IBR): The IBR register provisionally stores the right-hand instruction from the word in memory.

6. Program Counter (PC): The PC stores the memory address of the next instruction to be fetched for execution.

7. Accumulator (AC): An accumulator is a device that stores temporary operands and the results of any ALU operations.

Differences between Cache Memory and Register

Cache Memory and Register are two crucial components of a computer's memory structure, each uniquely enhancing CPU speed. Cache Memory is a secondary memory that saves frequently used data from the primary memory to minimize access time and boost CPU performance. On the other hand, a register is a form of internal memory that temporarily stores data that will be used by the CPU.

Cache Memory and Register are non-persistent (volatile) and maintained by the CPU, but they differ in size, location, access time, capacity, cost, kinds, purpose, and utilization. Cache Memory is larger and slower than Register but quicker than RAM, whereas Register is smaller and faster.

The CPU's memory controller manages cache memory, whereas the CPU manages registers and divides them into general-purpose and special-purpose registers.

Conclusion

In conclusion, Cache Memory and Register have several aspects that distinguish them from each other, including their persistence, management, types, function, and usage.

Overall, understanding the differences between Cache Memory and Register is crucial in designing efficient computer systems that can handle complex tasks quickly and effectively. By optimizing the use of these memory types, computer engineers can improve CPU performance and enhance the user experience.