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Show processors involves a history buffer [76]. The history buffer contains exactly the information needed by the history cache, although over a much shorter time period. The history buffer imposes as little as 3% overhead on the performance of the processor. Even if the history buffer is not implemented, the history might not impose any time overhead on the cache subsystem, since in many cache implementations the Read of a value from the cache can be done in parallel with the cache hit check [76]. Taking together the performance overhead on the processor and on the memory subsystem, the support for history should slow down the entire system at most 10% and probably less than 5% in practice. This overhead is insignificant in the light of the powerful new features enabled by the process history. 5.5 Summary This section summarizes main architectural features of an introspective computer (see Figure 5.15). Processor core is a regular processor. The processor is extended with a filter, a history buffer and interfaces for history cache, execution stream and 146 execution stream commands processor core mfilter execution stream history buffer processor commands history history cache storage Figure 5.15. Introspective Computer |
