Papers by Robert Chappell
Proceedings of the 24th annual international symposium on Computer architecture, 1997
Deeply pipelined, superscalar processors require accurate branch prediction to achieve high perfo... more Deeply pipelined, superscalar processors require accurate branch prediction to achieve high performance. Two-level branch predictors have been shown to achieve high prediction accuracy. It has also been shown that branch interference is a major contributor to the number of branches mispredicted by two-level predictors. This paper presents a new method to reduce the interference problem called agree prediction, which reduces the chance that two branches aliasing the same PHT entry will interfere negatively. We evaluate the performance of this scheme using full traces (both user and supervisor) of the SPECintgfi benchmarks. The result is a reduction in the misprediction rate of gee ranging from 8.62% with a 64Kentry PHT up to 33.3% with a IK-entry PHT.
ACM SIGARCH Computer Architecture News, 1998
Pipeline flushes due to branch mispredictions is one of the most serious problems facing the desi... more Pipeline flushes due to branch mispredictions is one of the most serious problems facing the designer of a deeply pipelined, superscalar processor. Many branch predictors have been proposed to help alleviate this problem, including two-level adaptive branch predictors and hybrid branch predictors.Numerous studies have shown which predictors and configurations best predict the branches in a given set of benchmarks. Some studies have also investigated effects, such as pattern history table interference, that can be detrimental to the performance of these predictors. However, little research has been done on which characteristics of branch behavior make predictors perform well.In this paper, we investigate and quantify reasons why branches are predictable. We show that some of this predictability is not captured by the two-level adaptive branch predictors. An understanding of the predictability of branches may lead to insights ultimately resulting in better or less complex predictors. ...
35th Annual IEEE/ACM International Symposium on Microarchitecture, 2002. (MICRO-35). Proceedings.
Research has shown that precomputation microthreads can be useful for improving branch prediction... more Research has shown that precomputation microthreads can be useful for improving branch prediction and prefetching. However, it is not obvious how to provide the necessary microarchitectural support, and few details have been given in the literature. By judiciously constraining microthreads, we can easily adapt a superscalar machine to support many simultaneous microthreads. The nature of precomputation microthreads also requires efficient usage of resources. Our proposed implementation addresses this issue by dynamically identifying and aborting useless microthreads.
The Journal of Prosthetic Dentistry, 1992
The in vitro physical properties of two types of polydimethyl siloxane, MDX 4-4210 and a new mate... more The in vitro physical properties of two types of polydimethyl siloxane, MDX 4-4210 and a new material A-2186, were compared. The properties that were investigated in this study were tensile strength, elongation, tear strength, and surface hardness. The properties tested were selected because of their clinical significance for fabricating a facial prosthesis. According to the results obtained in this investigation, the new material, A-2186, had greater tear resistance, tensile strength, and a larger percentage of elongation. A-2186 material, also proved to be softer at the surface than the MDX 4-4210. This combination of physical properties makes this material, A-2186, a better choice than the traditional MDX 4-4210 for the fabrication of facial prostheses.
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Papers by Robert Chappell