Register 读写只需要半个 cycle，先写再读

The OR instruction also operates without incurring a hazard because we perform the register file reads in the second half of the cycle and the writes in the first half

每个 cycle 都是先写再读的，那个实线和虚线的意思是，ID (Instruction Decode) 阶段用到的是读，发生在后半个 cycle（实线），WB (Write Back) 阶段需要写入 Register，发生在前半个 cycle（实线）。 因此图中的 OR Instruction 没有 data harzard。

X86/X64

byte (charactor): 8 bits R8b word: 8 * 2 bits (16) R8w double word: 8 * 4 bits (32) R8d quad word: 8 * 8 bits (64) R8

note:

• Rax, Rbx ..... R8 is for X64 (64-bit instruction)
• X86 have Eax, Ebx .... (32-bit instruction). For X64, the lower 32 bits of Rax, Rbx... are Eax, Ebx...

MIPS

byte (charactor): 8 bits half word: 8 * 2 bits (16) word: 8 * 4 bits (32) double word: 8 * 8 bits (64)