๐ง Bit-Width vs Addressable Space
๐น Bit-Width (Data Width)
Refers to the size of data units the processor natively handles.
| Property | Meaning | 16-bit Example |
|---|---|---|
| Register size | How many bits each register holds | AX = 16 bits = 2 bytes |
| ALU operand size | Bit-width of arithmetic/logical operations | ADD AX, BX โ operates on 16-bit values |
| Instruction encoding | Designed to work with 16-bit operands | MOV AX, [1234h] |
๐งฉ Think of this as the internal word size โ the granularity of computation.
๐น Addressable Space (Memory Reach)
Refers to how many distinct memory locations the processor can reference.
| Property | Meaning | 16-bit Example |
|---|---|---|
| Address bus width | Bits used to form memory addresses | 16-bit address โ 2ยนโถ = 65,536 addresses |
| Address granularity | Size of each addressable unit | Typically 1 byte per address |
| Total memory reach | Maximum directly addressable memory | 64 KB (if no segmentation/paging) |
๐งฉ This is about external reach โ how far the processor can point into memory.
โ Summary
- “16-bit processor” โ Refers to internal data width (registers, ALU, instruction operands)
- “2^16 bytes” โ Refers to external memory reach via 16-bit address bus
- These are related but distinct: one is about how wide, the other is about how far
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