Hardware Registers

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    • @devyncjohnson

    Registers are small amounts of memory or cache that a computer can use to store information. Many types of registers exist. Registers are the fastest type of memory in a computer system. However, they are more expensive to create than RAM chips. Therefore, there are not as registers as RAM.

    There are two types of processor registers, user-accessible registers and internal registers. User-accessible registers are the registers that the programs and code can access while internal registers can only be used by the CPU itself.

    Many types of user-accessible registers are available. Data registers are commonly used registers that can hold any type of data such as float-points, integers, characters, small arrays, etc. Address registers store addresses that point to need data on the RAM (commonly called the Primary Memory). General Purpose Registers (GPRs) are special registers that can store data or addresses. Conditional registers store boolean values and Float-Point Registers (FPRs) store float-point values. Constant registers are read-only registers that store constants, such as Pi. Model-Specific registers store settings that are specific to the CPU. Special Purpose Registers (SPRs) are registers that have special abilities such as a counter register which is a counter. Vector registers store vector data for SIMD instructions (Single Instruction, Multiple Data). Memory Type Range Registers (MTRRs) store information concerning how memory ranges are cached.

    Not as many internal registers exist as do user-accessible registers. Instruction registers store the data that is currently being executed.

    Video cards can also contain registers such as buffer registers which store data.

    The size of registers are measured in bits. For instance, an 8-bit register can store up to eight bits.

    Registers are made out of flip-flops. Flip-flops can be made from cross-coupled NOR logic gates, cross-coupled NAND logic gates, bipolar junction transistors, or other circuit configurations. Flip-flops can also be called "latches".

    Further Reading

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