Predecoding

• Do some predecoding as part of Instruction cache fill

  • Attaches extra bits to each instruction
  • Bits denominate the instruction class, type of resources required, and even calculation of branch target address
  • Number of extra bits range from 4 to 7 (table 7.1)

• Power PC 620 and R10000 use predecoding

  • Only one cycle for decoding and issue

• Some modern processors don’t use predecoding

  • Alpha 21116 and PentiumPro

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