Register Memory

Register memory is the smallest and fastest memory in a computer. It is not a part of the main memory and is located in the CPU in the form of registers, which are the smallest data holding elements. A register temporarily holds frequently used data, instructions, and memory address that are to be used by CPU. They hold instructions that are currently processed by the CPU. All data is required to pass through registers before it can be processed. So, they are used by CPU to process the data entered by the users.

Registers hold a small amount of data around 32 bits to 64 bits. The speed of a CPU depends on the number and size (no. of bits) of registers that are built into the CPU. Registers can be of different types based on their uses. Some of the widely used Registers include Accumulator or AC, Data Register or DR, the Address Register or AR, Program Counter (PC), I/O Address Register, and more.

Architecture of Register Memory

• This architecture is driven by instructions, through which operations are to be carried out on the registers and memory. The architecture is referred to as a register plus memory architecture if all of the operands are contained in the register.
• An operation can have two operands: one of them can be in memory and the other one in a register. On the other hand, the both operands of operation are either in the register or in the memory, which distinguishes it from other architectures.
• Examples of this memory are Intel x86 and IBM System/360.

• The numbers of registers in the CPU are fewer, and they are also small in size. Its size is fewer than 64 bits. It is quicker as compared to disk memory and primary memory. The size of general-purpose registers affects the word size.
• The computer provides instructions for the registration number and the register's address. Various register identifiers include R0, R1, R7, SP, and PC. A register serves as a connection point between a program and the system's data storage.

Types and Functions of Computer Registers:

The fetching, decoding, and execution operations are the three important roles that computer registers play. The register gathers and stores user-provided data instructions at the designated location. The instructions are deciphered and processed in order to provide the user with the desired output. To ensure that the user receives and understands the results as expected, the information must be thoroughly digested. The registers understand the tasks and store them in the computer's memory. The same is provided to a user upon their request. Processing is carried out in accordance with user requirements. The computer system uses a variety of registers to store data and reduce memory utilization. Every register used by the CPU has a unique function. The sorts of common registers are described below.

• Data Register: It is a 16-bit register, which is used to store operands (variables) to be operated by the processor. It temporarily stores data, which is being transmitted to or received from a peripheral device.
• Program Counter (PC): It holds the address of the memory location of the next instruction, which is to be fetched after the current instruction is completed. So, it is used to maintain the path of execution of the different programs and thus executes the programs one by one, when the previous instruction gets completed.
• Instructor Register: It is a 16-bit register. It stores the instruction which is fetched from the main memory. So, it is used to hold instruction codes, which are to be executed. The Control Unit takes instruction from Instructor Register, then decodes and executes it.
• Accumulator Register: It is a 16-bit register, which is used to store the results produced by the system. For example, the results generated by CPU after the processing are stored in the AC register.
• Address Register: It is a 12-bit register that stores the address of a memory location where instructions or data is stored in the memory.
• I/O Address Register: Its job is to specify the address of a particular I/O device.
• I/O Buffer Register: Its job is to exchange the data between an I/O module and the CPU.

Use of Register Memory

• The CPU may access frequently used data, instructions, and the address and location of all of these from the registers whenever needed. The register stores the instructions that the CPU will process. Prior to processing, every data must pass through the registers. Therefore, we can conclude that users enter data into registers to be processed by the CPU.
• The registers allow for the speedy acceptance, storage, and transmission of data, and any kind of register is utilized to carry out the precise tasks that the CPU requires. Users do not need to be very knowledgeable about the register because the CPU holds it as temporary memory and a data buffer.
• Registers act as buffers for copying data from main memory so that the processor can access it whenever it is needed. The data is kept in the register so that the register is aware of the location and address and can use that information in order to determine the IP addresses.
• According to the requirements, the base register can modify computer operations or operands, and in computer system instructions, the address portion may be added to the register.

Each CPU has a few bytes allotted to its registers. The register contains fast memory and instructions to work on the system. Since the compiler stores temporary data in the register rather than the RAM, through which programs run more quickly than they should in the system.

Why do we need register memory?

CPU registers are very helpful for handling instructions quickly. It is at the top of the hierarchy of computer memory and is significantly faster as compared to other computer memory. Any type of small data, including registers, addresses, and instructions, can be stored there. These registers enable the CPU to function effectively and meaningfully.

Difference between Cache Memory and Register

Although they both generally store data, cache memory and registers differ greatly from one another. All of a device's frequently used data and instructions are stored in the cache memory. As a result, it accelerates the computer's overall performance and operation as well. The register, on the other hand, only stores a single item of information, such as a computer instruction or the location of a specific piece of data.

Let's discuss the difference between register and cache memory. Below is given a table in which we are comparing the two terms on the basis of their unique characteristics to help make this topic more clear and more understandable.