Information about Wait State
A wait state is a delay experienced by a computer processor when accessing external memory or another device that is slow to respond.
As of late 2007, computer microprocessors run at very high speeds, while memory technology does not seem to be able to catch up: typical PC processors like the Intel Core 2 and the AMD Athlon 64 X2 run with a clock of several GHz, while the main memory clock ranges from 677 to 13 MHz. Some second-level CPU caches run slower than the processor core.
When the processor needs to access external memory, it starts placing the address of the requested information on the address bus. It then must wait for the answer, that may come back tens if not hundreds of cycles later. Each of the cycles spent waiting is called a wait state.
Wait states are a pure waste for a processor's performance. Modern designs try to eliminate or hide them using a variety of techniques: CPU caches, instruction pipelines, instruction prefetch, branch prediction, simultaneous multithreading and others. No single technique is 100% successful, but together they can significantly reduce the problem.
As of late 2007, computer microprocessors run at very high speeds, while memory technology does not seem to be able to catch up: typical PC processors like the Intel Core 2 and the AMD Athlon 64 X2 run with a clock of several GHz, while the main memory clock ranges from 677 to 13 MHz. Some second-level CPU caches run slower than the processor core.
When the processor needs to access external memory, it starts placing the address of the requested information on the address bus. It then must wait for the answer, that may come back tens if not hundreds of cycles later. Each of the cycles spent waiting is called a wait state.
Wait states are a pure waste for a processor's performance. Modern designs try to eliminate or hide them using a variety of techniques: CPU caches, instruction pipelines, instruction prefetch, branch prediction, simultaneous multithreading and others. No single technique is 100% successful, but together they can significantly reduce the problem.
See also
central processing unit (CPU), or sometimes simply processor, is the component in a digital computer capable of executing a program.(Knott 1974) It interprets computer program instructions and processes data.
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Computer data storage, computer memory, and often casually storage or memory refer to computer components, devices and recording media that retain digital data used for computing for some interval of time.
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Intel Corporation
Public (NASDAQ: INTC , SEHK: 4335 )
Founded 1968 1
Headquarters Santa Clara, California
United States
Key people Paul S.
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Public (NASDAQ: INTC , SEHK: 4335 )
Founded 1968 1
Headquarters Santa Clara, California
United States
Key people Paul S.
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Core 2
Central processing unit
Codename "Conroe"
Produced: From 2006
Manufacturer: Intel
CPU Speeds: 1.
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Central processing unit
Codename "Conroe"
Produced: From 2006
Manufacturer: Intel
CPU Speeds: 1.
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Advanced Micro Devices, Inc.
Public (NYSE: AMD )
Founded 1969
Headquarters One AMD Place
Sunnyvale, California
USA
Key people Héctor Ruiz, CEO
Industry Semiconductors
Products Microprocessors
Motherboard chipsets
DTV decoder chips
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Public (NYSE: AMD )
Founded 1969
Headquarters One AMD Place
Sunnyvale, California
USA
Key people Héctor Ruiz, CEO
Industry Semiconductors
Products Microprocessors
Motherboard chipsets
DTV decoder chips
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Athlon 64 X2 is the first dual-core desktop CPU manufactured by AMD. It is essentially a processor consisting of two Athlon 64 cores joined together on one die with additional control logic.
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GHZ or GHz may refer to:
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- Gigahertz (units of frequency).
- Greenberger-Horne-Zeilinger state (GHZ state) - a quantum entanglement of three particles.
- Galactic Habitable Zone - the region of a galaxy that is favorable to the formation of life.
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hertz (symbol: Hz) is the SI unit of frequency. Its base unit is cycle/s or s-1 (also called inverse seconds, reciprocal seconds). In English, hertz is used as both singular and plural.
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CPU cache is a cache used by the central processing unit of a computer to reduce the average time to access memory. The cache is a smaller, faster memory which stores copies of the data from the most frequently used main memory locations.
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An address bus is a computer bus, used by CPUs or DMA-capable units for communicating the physical addresses of computer memory elements/locations that the requesting unit wants to access (read/write).
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CPU cache is a cache used by the central processing unit of a computer to reduce the average time to access memory. The cache is a smaller, faster memory which stores copies of the data from the most frequently used main memory locations.
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instruction pipeline is a technique used in the design of computers and other digital electronic devices to increase their instruction throughput (the number of instructions that can be executed in a unit of time).
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In computer architecture, instruction prefetch is a technique used in microprocessors to speed up the execution of a program by reducing wait states.
Modern microprocessors are much faster than the memory where the program is kept, meaning that the program's instructions
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Modern microprocessors are much faster than the memory where the program is kept, meaning that the program's instructions
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branch predictor is the part of a processor that determines whether a conditional branch in the instruction flow of a program is likely to be taken or not. This is called branch prediction.
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Simultaneous multithreading, often abbreviated as SMT, is a technique for improving the overall efficiency of superscalar CPUs. SMT permits multiple independent threads of execution to better utilize the resources provided by modern processor architectures.
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In computing, a bubble is a "hiccup" in execution of an instruction in an instruction pipeline.
The following is two executions of the same four instruction through a 4-stage pipeline but, for whatever reason, a delay in fetching of the purple instruction in cycle #2 leads
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The following is two executions of the same four instruction through a 4-stage pipeline but, for whatever reason, a delay in fetching of the purple instruction in cycle #2 leads
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