This structure holds the instructions while they are waiting for their operands or they are executing in the corresponding FU.

Let T be a specific type of FU. There is an associated RE[T] for each type of FU. Let N[T] be the number of FU[T] and let P[T] be the number of pipeline stages of this FU. The number of entries of RE[T] is computed by using the following expression: N[T] * P[T] + 1

Fields

• Inst.: Instruction identifier.
• Qj: The ROB entry that will produce the first source operand. A value of -1 indicates that the source operand is already available in Vj.
• Vj: Value of the first source operand if (Qj = -1).
• Qk: The ROB entry that will produce the first source operand. A value of -1 indicates that the source operand is already available in Vk.
• Vk: Value of the first source operand if (Qk = -1).
• A: Memory address.
• ROB: ROB entry where this instruction is being processed.