Timing uncertainty in microprocessors is comprised of several sources including PLL jitter, clock distribution skew and jitter, across chip device variations, and power supply noise. The on-chip measurement macro called SKITTER (SKew+jITTER) was designed to measure timing uncertainty from all combined sources by measuring the number of logic stages that complete in a cycle. This measure of completed delay stages has proven to be a very sensitive monitor of power supply noise, which has emerged as a dominant component of timing uncertainty. This paper describes the Skitter measurement experiences of several IBM microprocessors including PPC970MP, XBOX360TM, CELL Broadband EngineTM, and POWER6TMmicroprocessors running different workloads.

Timing uncertainty in microprocessors is comprised of several sources including PLL jitter, clock distribution skew and jitter, across chip device variations, and power supply noise. The on-chip measurement macro called SKITTER (SKew+jITTER) was designed to measure timing uncertainty from all combined sources by measuring the number of logic stages that complete in a cycle. This measure of completed delay stages has proven to be a very sensitive monitor of power supply noise, which has emerged as a dominant component of timing uncertainty. This paper describes the Skitter measurement experiences of several IBM microprocessors including PPC970MP, XBOX360trade, CELL Broadband Enginetrade, and POWER6trade microprocessors running different workloads.

This paper addresses the problem of an efficient dispatch mechanism in an object-oriented system with multiple inheritance. The solution suggested is a direct table indexed branch such as is used in C++. The table slot assignments are made using a coloring algorithm. The method is applicable to strongly typed languages such as C++ (with multiple inheritance added) and Eiffel, and in a slightly slower form to less strongly typed languages like Objective C.