EEL 5708 Multiple Issue Challenges While Integer/FP split is simple for the HW, get CPI of 0.5 only for programs with: –Exactly 50% FP operations AND No hazards If more instructions issue at same time, greater difficulty of decode and issue: –Even 2-scalar => examine 2 opcodes, 6 register specifiers, & decide if 1 or 2 instructions can issue; (N-issue ~O(N 2 -N) comparisons) –Register file: need 2x reads and 1x writes/cycle –Rename logic: must be able to rename same register multiple times in one cycle.
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