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Topic: Simultaneous multithreading

	Simultaneous multithreading - Wikipedia, the free encyclopedia
		Simultaneous multithreading, often abbreviated as SMT, is a technique for improving the overall efficiency of the hardware that executes instructions in a computer.
		Normal multithreading operating systems allow multiple processes and threads to utilize the processor one at a time, giving exclusive ownership to a particular thread for a time slice in the order of milliseconds - this is called Temporal multithreading.
		The Intel Pentium 4 was the first modern commercial processor to implement simultaneous multithreading, starting from the 3.06GHz model released in 2002, and since introduced into a number of their processors.
	en.wikipedia.org /wiki/Simultaneous_multithreading (1047 words)

	Temporal multithreading - Wikipedia, the free encyclopedia
		Temporal multithreading is one of the two main forms of multithreading that can be implemented on computer processor hardware, the other form being Simultaneous multithreading.
		In Temporal multithreading the number is one, while in Simultaneous multithreading the number is larger than one.
		This form of multithreading can be more expensive than the coarse-grain forms because execution resources that span multiple pipe stages may have to deal with multiple threads.
	en.wikipedia.org /wiki/Temporal_multithreading (367 words)

	An Analysis of Computer Architectures For Exploiting Parallelism
		Simultaneous multithreading (SMT) is an architectural technique in which the processor issues multiple instructions from multiple threads in a single cycle [1].
		Simultaneous multithreading combines the multiple-issue-per-instruction features of modern superscalar processors with the latency-hiding ability challenges from these architectures, e.g., achieving high register file bandwidth, supporting high memory access demands, meeting large forwarding requirements, and scheduling instructions onto functional units [1].
		Simultaneous multithreading adds minimal hardware complexity to, and, in fact, is a straightforward extension of, conventional dynamically scheduled superscalar (it’s described in the following paragraph).
	longwood.cs.ucf.edu /~feuerbac/papers/archpara.html (5476 words)

	SMT resources: Press releases, academic papers, and presentations on Hyper-Threading and Chip-Multithreading technology (Site not responding. Last check: 2007-10-08)
		Simultaneous Multithreading: A Platform for Next-Generation Processors by Susan Eggers, Joel Emer, Henry M. Levy, Jack Lo, Rebecca Stamm, and Dean Tullsen.
		Simultaneous Multithreading and Multimedia by Heiko Oehring, Ulrich Sigmund, and Theo Ungerer.
		Multithreaded Microprocessors: Simultaneous Multithreading vs. Single-Chip Multiprocessing by Roxanne Canosa.
	www.princeton.edu /~jdonald/research/hyperthreading (2623 words)

	IBM JRD 49-4/5 \| Characterization of simultaneous multithreading (SMT) efficiency in POWER5
		Simultaneous multithreading (SMT), first available on the POWER5™ processor, moves beyond simple thread switching to the maintenance of two thread streams that are issued as continuously as possible to ensure the maximum use of processor resources.
		In general, multithreading can cause cache-miss rates to increase, but the overlap is usually more than enough to overcome this and still achieve significant increases in throughput [8].
		Simultaneous multithreading (SMT) is a way of implementing multiple threads on an out-of-order processor [9–11].
	www.research.ibm.com /journal/rd/494/mathis.html (5924 words)

	Real World Technologies - Alpha EV8 (Part 2): Simultaneous Multi-Threat
		But a coarse grained multithreaded processor has the opportunity to quickly switch to another thread after a cache miss and perform useful work while the first thread awaits its data from memory.
		The hardware cost of fine grained multithreading is relatively modest: N thread contexts, and control logic and multiplexors to cyclically commutate instructions and data from N different threads into and out of the execution units.
		Called Simultaneous Multithreading (SMT), it allows the instructions from two or more threads to be issued to execution units each cycle.
	www.realworldtech.com /page.cfm?ArticleID=RWT122600000000 (1280 words)

	An Analysis of Database Workload Performance on Simultaneous Multithreaded Processors (Site not responding. Last check: 2007-10-08)
		Simultaneous multithreading (SMT) is an architectural technique in which the processor issues instructions from multiple threads in a single cycle [1].
		Simultaneous multithreading is their answer to the best way of utilizing current and future processor design.
		Because simultaneous multithreaded processors successfully (and simultaneously) exploits both types of parallelism, SMT processors use resources more efficiently, and both instruction throughput and speedups are greater [2].
	longwood.cs.ucf.edu /~feuerbac/papers/smt-db.html (1813 words)

	Simultaneous Multithreading (Site not responding. Last check: 2007-10-08)
		This paper examines simultaneous multithreading, a technique permitting several independent threads to issue instructions to a superscalar's multiple functional units in a single cycle.
		Simultaneous multithreading has the potential to achieve 4 times the throughput of a superscalar, and double that of fine-grain multithreading.
		We also show that simultaneous multithreading is an attractive alternative to single-chip multiprocessors; simultaneous multithreaded processors with a variety of organizations outperform corresponding conventional multiprocessors with similar execution resources.
	www.cs.washington.edu /research/arch/mult-sim.html (220 words)

	CSEE Colloquium \| OGI School of Science & Engineering (Site not responding. Last check: 2007-10-08)
		Simultaneous multithreading (SMT) is a technique that combines superscalar execution with hardware multithreading.
		While traditional hardware multithreading architectures (e.g., Alewife, Tera) depend on fast context switches to time-share the processor, simultaneous multithreading permits multiple threads to issue instructions to a superscalar's functional units in the same cycle.
		Also, I will present an architecture for SMT which demonstrates that the performance potential of SMT can be realized without (1) excessive changes to a conventional superscalar design or (2) hurting single-thread performance in the limiting case where there is only one thread in the processor.
	www.cse.ogi.edu /colloquia/event/131.html (262 words)

	Simultaneous Multithreading home page
		Simultaneous multithreading is a processor design that combines hardware multithreading with superscalar processor technology to allow multiple threads to issue instructions each cycle.
		Unlike other hardware multithreaded architectures (such as the Tera MTA), in which only a single hardware context (i.e., thread) is active on any given cycle, SMT permits all thread contexts to simultaneously compete for and share processor resources.
		Simultaneous multithreading has already had impact in both the academic and commercial communities.
	www.cs.washington.edu /research/smt (1792 words)

	Simultaneous multithreading at opensource encyclopedia (Site not responding. Last check: 2007-10-08)
		The number of concurrent threads can be decided by the chip designers, but practical restrictions on chip complexity usually limit the number to 2, 4 or sometimes 8 concurrent threads.
		The only commercial processor using simultaneous multithreading is the Intel Pentium 4, starting from the 3.06 GHz model, and since introduced into a number of their processors.
		Sun refers to the concept as "throughput", a somewhat misleading terminology.
	www.wiki.tatet.com /Simultaneous_multithreading.html (428 words)

	University Week: Technology developed on campus will speed up computers
		The technique, known as simultaneous multithreading, was first proposed in the mid-1990s by Susan Eggers and Hank Levy, UW professors in the Department of Computer Science and Engineering.
		The concept of multithreading was first proposed in the 1960s and is used in supercomputers.
		Ultimately, Cray’s Smith predicts, multithreading of one sort or another will be needed for all types of computing, from personal computing to the very highest performance computing we do.
	depts.washington.edu /uweek/archives/2002.05.MAY_23/news_a.html (827 words)

	[No title] (Site not responding. Last check: 2007-10-08)
		They show that these two techniques (fine-grain multithreaded, and single-threaded superscalar architectures) are limited in their ability to actually use the resources available with a wide-issue processor.
		According to the authors, simultaneous multithreading has the capability to achieve a four-fold increase in throughput of a superscalar, and a two-fold increase over a fine-grain multi-threaded system.
		They conclude that simultaneous multithreading is a good option, with benefits over single-chip multiprocessors, since "simultaneous multithreaded processors with a variety of organizations outperform corresponding conventional multiprocessors with a similar execution resourses."
	www.cs.hmc.edu /~jsmallma/cs110/abstract10.html (282 words)

	US-CERT Vulnerability Note VU#911878
		Operating systems on hardware platforms supporting simultaneous multi-threading (Hyper-Threading technology in particular) are potentially vulnerable to information leakage to local users.
		This vulnerability is applicable to many operating system platforms running on a hardware platform that supports simultaneous multithreading (Intel HTT in particular).
		Disabling of simultaneous multithreading/HTT support at the operating system or BIOS level may reduce the likelihood of successful attack using the methods outlined in Colin's paper, however it may not mitigate against other similar types of attackes.
	www.kb.cert.org /vuls/id/911878 (487 words)

	Parallelization Strategies for Commodity Hardware (Site not responding. Last check: 2007-10-08)
		The achieved speedups for Symmetric Multiprocessing and Simultaneous Multithreading are shown in Figure 5.2.
		Testing Simultaneous Multithreading on only one CPU showed an average speedup of 30%.
		Figure 5.3 shows the Simultaneous Multithreading speedup for different block sizes.
	www.cg.tuwien.ac.at /~bruckner/homepage/content/mastersthesis/html/node58.html (309 words)

	Simultaneous Multithreading
		Simultaneous Multithreading is a well-known concept in workstation and mainframe hardware.
		Executing two threads simultaneously on one processor has the advantage of more independent instructions being available, and thus leads to more efficient CPU utilization.
		Then it has to choose the lists of blocks which can be processed simultaneously, with respect to the eight to distinguish viewing directions.
	www.cg.tuwien.ac.at /~bruckner/homepage/content/mastersthesis/html/node42.html (586 words)

	[No title]
		Back in the dual-Celeron days, when symmetric multiprocessing (SMP) first became cheap enough to come within reach of the average PC user, many hardware enthusiasts eager to get in on the SMP craze were asking what exactly (besides winning them the admiration and envy of their peers) a dual-processing rig could do for them.
		Years later when Apple brought dual-processing to its PowerMac line, SMP was officially mainstream, and with it multithreading became a concern for the mainstream user as the ensuing round of benchmarks brought out the fact you really needed multithreaded applications to get the full benefits of two processors.
		Even though the PC enthusiast SMP craze has long since died down and, in an odd twist of fate, Mac users are now many times more likely to be sporting an SMP rig than their x86-using peers, multithreading is once again about to increase in importance for PC users.
	arstechnica.com /articles/paedia/cpu/hyperthreading.ars/1 (1279 words)

	Simultaneous Multithreading Performance (Site not responding. Last check: 2007-10-08)
		Simultaneous multithreading (SMT) is a technique for improving CPU performance, where one CPU pretends to be two.
		Sun calls this paradigm shift "throughput computing," which is a name that I feel is relatively descriptive.
		Web serving is naturally a parallel activity, and it would be an interesting challenge to figure out to best scale its single thread of execution to multiple threads.
	evanjones.ca /smt-performance.html (580 words)

	Symbiotic jobscheduling with priorities for a simultaneous multithreading processor (Site not responding. Last check: 2007-10-08)
		Simultaneous Multithreading machines benefit from jobscheduling software that monitors how well coscheduled jobs share CPU re-sources, and coschedules jobs that interact well to make more ef-ficient use of those resources.
		Naive priority schedulers dedicate the machine to high priority jobs to meet prior-ity goals, and as a result decrease opportunities for increased per-formance from multithreading and coscheduling.
		More informed schedulers, however, can dynamically monitor the progress and re-source utilization of jobs on the machine, and dynamically adjust the degree of multithreading to improve performance while still meeting priority goals.
	www.cs.toronto.edu /~demke/OS_Reading_Grp/s2002/Abstracts/snavely02_abs.html (253 words)

	Abstract (Site not responding. Last check: 2007-10-08)
		In this paper we describe the principles of the chip multiprocessor architecture, overview design alternatives and present some example processors of this type.
		We discuss the results of several simulations where chip multiprocessor was compared to other advanced processor architectures including superscalars and simultaneous multithreading processors.
		Although simultaneous multithreading seems to be most efficient when compared architectures have equal total issue bandwidth, chip multiprocessor may outperform simultaneous multithreading when implemented with equal number of transistors.
	www-csd.ijs.si /abstracts/BR01A.html (128 words)

	Simultaneous Multithreading home page
		We have introduced and studied Simultaneous Multithreading (SMT), a technique that permits multiple independent threads to issue instructions to a superscalar's functional units in a single cycle.
		On an SMT processor, all hardware contexts are active simultaneously, competing each cycle for all available resources.
		Our studies have demonstrated that simultaneous multithreading significantly improves processor throughput and performance on both multiprogrammed and parallel workloads.
	www.ra.informatik.uni-stuttgart.de /~rainer/Lehre/PR99/SMT (579 words)

	Clearwater Networks - Simultaneous Multithreading (SMT) Core (Site not responding. Last check: 2007-10-08)
		This core incorporates Dynamic Multistreaming (DMS), or Simultaneous Multithreading (SMT) capabilities, whereby eight threads execute simultaneously, utilizing a variable number of resources on a cycle by cycle basis.
		In each cycle anywhere from zero to three instructions can be executed from each of the threads depending on instruction dependencies and availability of resources.
		The company was established to develop a network processor utilizing the multithreading technology that Mario Nemirovsky had pioneered.
	www.cs.ucla.edu /~tomyeh/clearwater.htm (512 words)

	Intel hyperthreading shows Digital roots \| CNET News.com
		Intel's hyperthreading, which involves breaking up an application for easier digestion by a computer's processors, derives in part from work on simultaneous multithreading performed by a team of researchers at the University of Washington and Digital, an Intel representative confirmed.
		Simultaneously, Intel hired a number of the Digital engineers and gradually began to incorporate the company's technology into its own product lines.
		In true Digital style, the Alpha chips that were to feature multithreading and integrated controllers have been delayed several times.
	news.com.com /2100-1001-961495.html (1388 words)

	OS Scheduling for Simultaneous Multithreading Processors (Site not responding. Last check: 2007-10-08)
		Within recent years the concept of the simultaneous multithreading (SMT) processor has been gaining in popularity.
		This hardware allows multiple processes to run on the processor at the same time providing more potential for instruction level parallelism.
		In contrast, the few number of decisions to make (few threads and/or few processes) the less important the decision of a scheduler becomes.
	www.eecs.harvard.edu /~jonathan/wisc/cs752 (230 words)

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