Processors except the CPU


SPMD model implemented by a SIMD processor

  • SIMD: a single sequential instruction stream of SIMD instruction
  • SIMT: Multiple instruction streams of scalar instructions

Grouping thread into warp --> advantage of SIMD
Independent execution of threads --> advantage of SPMD


  • simple hardware (no dynamic scheduling, dependency checking)
  • compilation (complex and recompilation is needed for various thing, width, latency changes)
  • lockstep execution causes independent operations to stall

DAE (Decoupled Access / Execute)

Motivation: Tomasulo's algorithm is too complex
Decouple Access (memory) / Execute (computing), communicate with queue

  • Queues reduce registers
  • OoO without wakeup/select complexity
  • Branch synchronization between A and E
  • multiple instruction streams?