4 ms·
The plumbing around the BX/BH-BL registers is something I'd love to look at. BX, BP, SI, and DI were the only registers available for indexable operations (thin
by EvanAnderson 6y ago
The plumbing around the BX/BH-BL registers is something I'd love to look at. BX, BP, SI, and DI were the only registers available for indexable operations (think "MOV WORD PTR [BX+2], AX"), and I wonder if the genesis of this behavior sits at the register file, or further away. BX/BH-BL is the only register capable of being used for indexable operations that is also 8-bit addressable.
- drmpeg 6y agoA byte addressable index register was required for 8080 assembly language compatibility to the H and L registers.
- EvanAnderson 6y agoBy "genesis of this behavior" I meant the implementation, not the reason (spec) for the behavior.