How do RISC and CISC differ in memory access?

RISC allows only LOAD and STORE to access memory; many CISC instructions can access memory directly

RISC allows all instructions to access memory

CISC allows only LOAD and STORE

Neither accesses memory directly

Which pair correctly describes RISC instructions?

Fixed length and mostly one clock cycle

Variable length and many cycles

Variable length and always one cycle

Where does each approach place the complexity?

RISC in the compiler (software), CISC in the hardware

RISC in the hardware, CISC in the compiler

RISC uses a hardwired control unit and gives larger programs; CISC is microprogrammed with smaller programs

RISC is microprogrammed with smaller programs

CISC is hardwired with larger programs

RISC has small register file and microcode

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Compare RISC and CISC architecture

Short answer

RISC uses simple fixed-length instructions with load/store architecture and a large register file, while CISC uses complex variable-length instructions with direct memory access. RISC has hardwired control and easy pipelining; CISC has microprogrammed control and smaller code size.

Compare and contrast RISC and CISC architecture.

RISC (Reduced Instruction Set Computer) uses a small set of simple, fixed-length instructions that mostly execute in one clock cycle. CISC (Complex Instruction Set Computer) uses a large set of complex, variable-length instructions, where one instruction can do many low-level operations.

Basis	RISC	CISC
Instruction set	Small, simple (about 50–150)	Large, complex (200+)
Instruction length	Fixed (e.g. 32 bits)	Variable
Execution time	Mostly 1 clock cycle	Several clock cycles
Addressing modes	Few, simple	Many
Memory access	Only LOAD and STORE access memory (load/store architecture)	Many instructions can access memory directly
Registers	Large register file (32 or more)	Few registers
Control unit	Hardwired (fast, simple)	Microprogrammed
Pipelining	Easy and efficient	Difficult
Code size	Larger programs (more instructions)	Smaller programs
Compiler	Complex compiler work; simple hardware	Simple compiler; complex hardware
Power / chip area	Low power, smaller control section	Higher power
Examples	ARM, MIPS, SPARC, PowerPC, RISC-V	Intel x86 (8086), Motorola 68000, VAX

Example: to add two memory numbers, CISC uses one instruction such as ADD [A], [B] (in a memory-to-memory machine); RISC uses LOAD R1,A; LOAD R2,B; ADD R3,R1,R2; STORE R3,C.

Contrast in short: RISC moves complexity to the software (compiler) so the hardware is simple and fast; CISC puts complexity in the hardware to reduce program size and compiler work. Modern x86 processors translate CISC instructions into RISC-like micro-operations internally.

✓ Answer checked by Claude Opus 5.5 (high effort)

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