Research On Fetch Control Mechanism Based On SMT Processors

With the development of computer architecture, the simultaneous multi-threadingprocessor came out and became the most important microprocessor to satisfy the urgent needin high performance processors. While the studies of the simultaneous multi-threadingprocessor become more and more popular, the fetch control mechanism are paid more andmore attention as the research hotspot. Recent years, professors home and abroad and researchinstitutions do a wide and deep research in this aspect. But there are also problems ofunbalanced fetch bandwidth、high collision rate of instruction queue and low performance ofbranch prediction in fetch control of it. So, this paper does research in the technology of fetchcontrol of the simultaneous multi-threading processor to research a more reasonable fetchcontrol mechanism.There are two aspects in this paper, the researches of fetch strategy and branch predictor.Also, a kind of fetch strategy and one branch predictor are proposed.Comparing with thetraditional fetch strategy, this one have some advantages in technology. The first one is thatthe usage of bandwidth is more balanced by distributing fetch process into three stages ofthread selection、 fetch bandwidth partition and dynamic resource allocation in whichallocating instruction band width by the calculated numbers of instructions needed by theactive threads.Meanwhile, the system resource utilization is improved by allocating thesystem resource by the priority. Based on the research of the new fetch strategy, a matchingbranch predictor was designed, by combining the global and part history thread information asthe information set of predicting branch to overcome the shortages of chaos and incompletebranch prediction information existed in traditional mechanism. Meanwhile, a Branch resulttable (BRT) is added to record the prediction result from that common prediction instructionsto promote the instruction branch predict execution speed. From the researches of this twoaspects, a fetch control mechanism based on the simultaneous multi-threading is proposedwhich can effectively improve the instruction throughput and performance of branchprediction of processor.At last, performance test and results analysis of this new theory were done throughdesigning the reasonable performance test method. The result of performance test resultshows that this new fetch mechanism can effectively overcome the shortages of low optimalfetch strategy and low performance in branch prediction and can contribute significantly toenhancing the overall performance of the processor and have a good application prospects and research value.