Performance Characterization of Mobile-Class Nodes: Why Fewer Bits is Better

1. Performance Characterization of Mobile-Class Nodes: Why Fewer Bits is Better Michelle McDaniel and Kim Hazelwood University of Virginia Mobile-class nodes---small, low power netbooks with limited available memory---are becoming increasingly popular in the personal computing market. Though originally designed with a 32-bit processor, these netbooks are now being shipped with a 64-bit mobile-class processor. We explore a variety of performance differences between mobile-class processors and server-class processors. Using the SPEC CPU2006 integer benchmarks, we show that the mobile-class processors do not benefit from the move to 64 bits like server-class processors do. We show that the limited memory available on these mobile-class nodes, along with the in-order nature of the processors, produce the greatest disparity in performance. Mobile-Class vs. Server-Class • Mobile Class: • In-order processor • Main focus: low power, high performance-per-watt • Less RAM • Smaller L2 cache • Server Class: • Out-of-order processor • Focus: performance with power as a secondary consideration • More RAM • Larger L2 cache Results Summary • libquantum • Mobile-Class node: 38% decrease in IPC from 32-bit to 64-bit mode • Server-Class node: 58% decrease in IPC from 32-bit to 64-bit mode • hmmer • Mobile-Class node: 4% decrease from 32-bit to 64-bit mode • Server-Class node: 56% increase from 32-bit to 64-bit mode