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Characteristics of RISC
Short answer
RISC uses a small simple fixed-length instruction set, load/store memory access, few addressing modes, many registers, hardwired control, single-cycle execution, efficient pipelining, and relies on compiler optimization. Examples: ARM, MIPS, RISC-V.
Write the characteristics of RISC.
RISC (Reduced Instruction Set Computer) processors are designed for simplicity and speed. Their main characteristics are:
- Small, simple instruction set: a limited number of simple instructions, often fewer than 100.
- Fixed-length instructions: all instructions have the same size (for example 32 bits), so decoding is simple and fast.
- Single-cycle execution: most instructions complete in one clock cycle.
- Load/store architecture: only LOAD and STORE instructions access memory; all other operations work on registers.
- Large register file: many general-purpose registers (32 or more) to reduce memory access; some designs use overlapping register windows.
- Few addressing modes: only simple modes such as register and register-plus-offset.
- Hardwired control unit: control signals are generated by logic gates instead of microcode, so the control is faster.
- Efficient pipelining: because instructions are uniform, instruction pipelines work well and give high throughput.
- Compiler optimisation: the compiler does much of the work (instruction scheduling, register allocation).
- Low power and smaller chip area: the simple control unit leaves area for registers and cache.
Examples: ARM, MIPS, SPARC, PowerPC, RISC-V.
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