Super-threading

Super-threading (or time-slice multithreading) is a type of multithreading that enables different threads to be executed by a single processor without truly executing them at the same time.^[1] This qualifies it as time-sliced or temporal multithreading rather than simultaneous multithreading (SMT). It is motivated by the observation that the processor's functional units are occasionally left idle while executing instructions from one thread due to long-latency events. Super-threading seeks to make use of the otherwise unused processor cycles by executing instructions from another thread until the previous thread is ready to resume execution.

While this approach enables better use of the processor's resources, further improvements to resource utilization can be realized through SMT, which allows the execution of instructions from multiple threads at the same time. Consider a two-way super-threaded processor with four functional units. If thread one issues three instructions, one functional unit remains unused. In an SMT processor, it is possible for thread two to issue an instruction to the remaining unit, attaining full utilization of processor resources.

References

↑ Superthreading with a multithreaded processor

CPU technologies

Architecture	Von Neumann Harvard (Modified Harvard) Dataflow TTA

Instruction set	ASIP CISC RISC EDGE EPIC MISC OISC VLIW NISC ZISC TRIPS Comparison

Word size	1-bit 4-bit 8-bit 9-bit 10-bit 12-bit 15-bit 16-bit 18-bit 22-bit 24-bit 25-bit 26-bit 27-bit 31-bit 32-bit 33-bit 34-bit 36-bit 39-bit 40-bit 48-bit 50-bit 60-bit 64-bit 128-bit 256-bit 512-bit Variable

Execution	Instruction pipelining Bubble Operand forwarding Out-of-order execution Register renaming Speculative execution Branch predictor Memory dependence prediction Hazards

Parallel level	Bit Bit-serial Word Instruction Scalar Superscalar Task Thread Process Data Vector Memory

Multithreading	Temporal Simultaneous Preemptive Cooperative

Flynn's taxonomy	SISD SIMD MISD MIMD SPMD Addressing mode

Types	Digital signal processor (DSP) GPGPU Microcontroller Physics processing unit System on a chip (SoC) Cellular

Components	Address generation unit (AGU) Arithmetic logic unit (ALU) Barrel shifter Floating-point unit (FPU) Back-side bus Multiplexer Demultiplexer Registers Memory management unit (MMU) Translation lookaside buffer (TLB) Cache Register file Microcode Control unit Clock rate

Power management	APM ACPI Dynamic frequency scaling Dynamic voltage scaling Clock gating

CPU hardware security	Non-executable memory (NX bit) Bounds checking (Intel MPX) Hardware restriction (firmware) Trusted Execution Technology Secure cryptoprocessor Hardware security module Hengzhi chip

Parallel computing

General	Distributed computing Cloud computing High-performance computing

Levels	Bit Instruction Task Data Memory

Multithreading	Temporal Simultaneous Preemptive Cooperative

Theory	PRAM model Analysis of parallel algorithms Amdahl's law Gustafson's law Cost efficiency Karp–Flatt metric Slowdown Speedup

Elements	Process Thread Fiber Instruction window

Coordination	Multiprocessing Memory coherency Cache coherency Cache invalidation Barrier Synchronization Application checkpointing

Programming	Models Implicit parallelism Explicit parallelism Concurrency Non-blocking algorithm

Hardware	Flynn's taxonomy SISD SIMD MISD MIMD Pipelined processor Superscalar processor Vector processor Multiprocessor symmetric asymmetric Memory shared distributed distributed shared UMA NUMA COMA Massively parallel computer Computer cluster Grid computer

APIs	POSIX Threads OpenMP OpenCL OpenHMPP OpenACC MPI PVM UPC TBB Boost.Thread Global Arrays Ateji PX Charm++ Cilk Coarray Fortran CUDA Dryad C++ AMP PLINQ TPL

Problems	Embarrassingly parallel Software lockout Scalability Race condition Deadlock Livelock Starvation Deterministic algorithm Parallel slowdown

Category: parallel computing Media related to parallel computing at Wikimedia Commons

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Super-threading

See also

References