Computer Science – Computer architecture | e-Consult
Computer architecture (1 questions)
The Instruction Set Architecture (ISA) defines the set of instructions that a CPU can understand and execute. It's essentially the interface between the hardware and the software. The ISA specifies:
- The instruction set: The specific instructions the CPU can execute (e.g., add, subtract, load, store).
- Data types: The types of data the CPU can work with (e.g., integers, floating-point numbers).
- Addressing modes: How the CPU can access memory locations (e.g., direct addressing, indirect addressing).
- Register set: The number and types of registers available to the CPU.
How a different ISA affects software: Software is written for a specific ISA. If a different ISA is used, the software will not run without significant modification or recompilation. This is because the software relies on the specific instructions and addressing modes defined by the ISA. A program compiled for one ISA will not be directly executable on a CPU with a different ISA.
Example: RISC vs. CISC
CISC (Complex Instruction Set Computing): CPUs with a CISC architecture have a large and complex instruction set. Instructions can perform multiple operations in a single instruction. Examples include Intel x86 processors.
RISC (Reduced Instruction Set Computing): CPUs with a RISC architecture have a smaller and simpler instruction set. Instructions are typically simpler and execute in a single clock cycle. Examples include ARM processors.
Feature CISC (e.g., x86) RISC (e.g., ARM) |
Instruction Set Size Large Small |
Instruction Complexity Complex (can perform multiple operations) Simple (typically one operation per instruction) |
Clock Cycles per Instruction Variable (can take multiple cycles) Fixed (typically one cycle) |