Cache and Registers

Cache memory
Cache is a smaller and fast memory component in the computer which is inserted between the CPU and the main memory. Cache memory is extremely fast memory and it resides within the processor chip (CPU). The main aim is to try to fill it with the data which might be needed again soon.

The cache must know where the information stored in a cache line originates from in main memory. It uses a directory store to hold the address identifying where the cache line was copied from main memory.

The size of a cache is defined as the actual code or data the cache can store from main memory.

Registers
Register are the smallest holding data elements that are built into processor itself. These are memory locations that can be directly accessible by processor. A register is basically a storage space for units of memory that are used to transfer data for immediate use by the CPU for data processing.

The register memory indicates the capacity of the register to hold the size of data it can hold. The capacity varies on the design of the processor and varies for example a 32-bit microprocessor can have 8-bit register giving memory size 256 bits. There are many types of registers like Accumulator, Data Register, Program Counter, General purpose, etc. Thus they can be used for various tasks.

CPU registers

The microprocessor chip serves as the central processing unit (CPU). It contains a clock that regulates the flow of data and instructions (each instruction takes a certain number of clock cycles to execute).

There is also an index register that keeps track of the instruction being executed. A small number of locations called registers within the CPU allow for storing or retrieving the data being used by instructions much more quickly than retrieval from main memory (RAM).

CPU registers is an important microarchitectural component used for storing operands and results of instructions. The design and operation of CPU registers has crucial impact on the performance, energy efficiency and reliability of the processor and hence, several techniques have been recently proposed to manage RF in modern processors.

The register file is an integral part of the CPU and as such is clearly defined in the architecture. The register can provide operands directly to the ALU (arithmetic logic unit).

Memory reference instructions load or stored data to/from the registers contained in the register files. The register file of the CPU holds the values for GPRs (General-purpose registers) and floating-point registers (FPRs). Additional registers for CPU control and addressing information are generally provided.

Typically, the instruction register advances to the next instruction. The instruction is fetched, decoded and sent to the CPU’s ALU for processing.
CPU registers