Status: Tags: #cards/cmpt295/isa Links: Instruction Set Architecture (ISA)
Instruction Set
Principles
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- All commands understood by agiven computer architecture
- Microprocessor implements an ISA
Guidelines
Unambiguous Encoding
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- the processor can easily decode and execute instructions
- in assembly, each instruction has specific naming schemes that translate directly into machine instructions
- this is done with the opcode and operand format
Functionality complete
Turing complete must have ?
- Data transfer instructions (memory reference)
- Data manipulation instructions (arith, logical)
- Program control instructions (branch, jump)
Brief machine instruction format
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- Few as possible
- Have all same length and format
- Position fields that have same purpose in same location in format
- src is always second
- if the format is different, the fields (sections) of your binary code must be formatted so the fields with the same purpose are at the same location
Types
Assembly Instruction ?
- Symbolic representation of machine instruction
- ex) movq
- Labels to represent adresses
Machine Instruction ?
- Each assembly instruction has corresponding machine instruction
- Represented as binary
CISC ?
- Complex instruction set computing
- Large # of instructions including special purpose
- usually register-memory architecture
- *ex) VAX, x86, MC68000`
RISC ?
- Reduced instruction set computing
- Small # of general purpose instructions
- Smaller machine instruction set
- Simpler microprocessor design
- Load/store architecture
- Only load/store can access memory
Components
Opcode ?
- Operation that can be executed by microprocessor
Operands ?
- Required by opcode for microprocessor to carry out instruction
- Expressed as binary
opcode | operands
References:
Created:: 2022-03-14 03:55