Dataflow processors - Hybrids
Poor sequential code performance by dynamic dataflow computers
- an instruction of the same thread is issued to the dataflow pipeline after the completion of its predecessor instruction.
- In the case of an 8-stage pipeline, instructions of the same thread can be issued at most every eight cycles.
- Low workload: the utilization of the dataflow processor drops to one eighth of its maximum performance.
Another drawback: the overhead associated with token matching.
- before a dyadic instruction is issued to the execution stage, two result tokens have to be present.
- The first token is stored in the waiting-matching store, thereby introducing a bubble in the execution stage(s) of the dataflow processor pipeline.
- measured pipeline bubbles on Monsoon: up to 28.75 %
No use of registers possible!