Performance Briefs
Hyper-Threading
Paul Martin (). Updated 3/27/2003
Summary: The effect of Hyper-Threading on performance varies greatly and is difficult to predict. While there are benefits as high as 15-35% in specific scenarios, there can be negative benefits in some scenarios. Careful evaluation is required.
Background: Intel’s Hyper-Threading (HT) is technology that adds a small amount of logic (“Architectural State”) to the CPU to create two “logical” processors and better utilize the CPU resources. HT is currently defaulted off on all HP Workstation platforms and is only recommended for WinXP and Redhat 7.1 or later. It is trivial to turn on/off in the boot-time Setup screen, and is available on almost all Xeon and Pentium-4 Workstation platforms starting in May 2003.
Results: Initial HT results were disappointing, but Intel has significantly improved results in certain cases. Performance improvements vary dramatically and in many cases no benefit or even negative benefits are observed. Two scenarios currently show significant positive benefits: (1) Multi-tasking and (2) Multi-threaded apps, especially ones optimized for HT. – this chart represents best case results (data from Intel).
Conclusion: For users that are working primarily with one application at a time, especially if that application is graphics-intensive – probably leave HT off. For users that know that they have an application that is optimized for HT (and Intel is helping ISVs grow this list) or that do multiple concurrent tasks such as multiple compiles, virus scans in background, or encoding in background, HT could be useful. In these cases it is still important to judge the system interactiveness with HT on / off.
Links
Hyper-Threading and HP Workstations http://tclperf.fc.hp.com/performance_briefs/docs/2003-04-09HT_in_UP_DP.doc
Intro to Hyper-Threading Technology http://www.intel.com/technology/hyperthread/download/25000802.pdf
Source: Intel Corporation. With and without Hyper-Threading Technology on the following system configuration: Intel Xeon Processor 2.80 GHz/533 MHz system bus with 512KB L2 cache, Intel® E7505 chipset-based Pre-Release platform, 1GB PC2100 DDR CL2 CAS2-2-2, (2) 18GB Seagate* Cheetah ST318452LW 15K Ultra160 SCSI hard drive using Adaptec 39160 SCSI adapter BIOS 3.10.0, nVidia* Quadro4 Pro 980XGL 128MB AGP 8x graphics card with driver version 40.52, Windows XP* Professional build 2600. Performance tests and ratings are measured using specific computer systems and/or components and reflect the approximate performance of Intel products as measured by those tests. Any difference in system hardware or software design or configuration may affect actual performance. Buyers should consult other sources of information to evaluate the performance of systems or components they are considering purchasing. For more information on performance tests and on the performance of Intel products, visit http://www.intel.com/performance/resources/limits.htm or call (U.S.) 1-800-628-8686 or 1-916-356-3104.