Introduction - Compaq Evo W8000 Supplementary Manual

Analysis of Intel Xeon Processor Frequency Grades and Cache Sizes on Performance Benchmarks White Paper

Introduction

Computer performance is highly dependent on key system features. Processor speed, memory
bandwidth, graphics cards, and disk drives all play important roles in determining system
performance. Highly computationally intensive tasks can benefit from higher frequency
processors. A larger cache on the processors can reduce the number of memory accesses and
increase system performance on applications that have small data sets (those that can reside on
the processor cache). Applications that require very large files use many disk accesses and require
more optimization in that area. Memory bandwidth is a crucial factor in getting the data quickly
to the processor. This paper will focus mainly on system processor performance.
A good measure of performance is the amount of time it takes to execute a given application.
Contrary to popular belief, clock frequency (MHz) and the number of instructions executed per
clock (IPC) are not fair indexes of performance by themselves. True performance is a
combination of both clock frequency (MHz) and IPC.
Performance = Frequency x IPC
The formula: Performance = Frequency x IPC means that performance can be improved by
increasing frequency, IPC or both. Frequency is a function of both the manufacturing process and
the micro-architecture. At any given clock frequency, the IPC is a function of processor micro-
architecture and the specific application being executed. Although it is not always feasible to
improve both the frequency and the IPC, increasing one and holding the other close to constant
with the prior generation provides a significantly higher level of performance.
In addition to these two methods for increasing performance, it is also possible to increase
performance by reducing the number of instructions that it takes to execute a specific task. Single
Instruction Multiple Data-Stream (SIMD) is a technique used to accomplish this. This is done
using 128-bit SIMD single-precision floating-point Streaming SIMD Extensions (SSE).
This analysis will discuss the performance differences between different speeds of the previous
Intel Xeon .18 processor (Foster) and new Intel Xeon .13 Processor (Prestonia). This paper will
also analyze how the larger cache on Xeon .13 determines system performance.
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