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Isolated I/O vs memory-mapped I/O
Short answer
Isolated I/O uses separate address spaces and special IN/OUT instructions, while memory‑mapped I/O shares the common memory address space and uses regular load/store instructions. Isolated I/O reserves the full memory range but needs extra control lines; memory‑mapped I/O simplifies hardware at the cost of reduced memory address space.
Differentiate between isolated I/O and memory-mapped I/O.
| Point | Isolated I/O | Memory-mapped I/O |
|---|---|---|
| Address space | Separate address spaces for memory and I/O | One common address space shared by memory and I/O |
| Control signals | Separate: IORD, IOWR and MEMRD, MEMWR | Same memory read/write signals |
| Instructions | Special instructions: IN, OUT | Ordinary memory instructions: LOAD, STORE, MOV |
| Address space for memory | Full address space available | Reduced by the I/O addresses |
| Hardware | More control lines and decoding for I/O | Simpler hardware |
| Programming | Less flexible, limited instructions | All memory instructions, including arithmetic, work on I/O |
| Example | Intel 8085/8086 with IN/OUT | Motorola 68000, ARM |
✓ Answer checked by Claude Opus 5.5 (high effort)
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