Coherency Granule
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Coherency Granule
In computers it is typical to define rules relative to data transfers for optimizing the overall system considerations. One such consideration is to define coherency granules (CG) that relate to units of data that are stored in memory. These units generally have a close relationship to caches that may be used in the system. The Coherency Granule size typically corresponds to the cache line size in a computer system.Computer Architecture: A Quantitative Approach, John L. Hennessy, David A. Patterson, Elsevier, 2012 The hardware is designed with the assumption that coherency granules will be the data packets that are typically transferred in a cache coherent system when accessing coherent data. The magnitude of the coherency granule is typically significantly greater than the bus size. For example, in current processing systems, the coherency granule is commonly 32 bytes, and the bus size is 8 bytes wide. In such a case, a data transfer of one coherency granule requires 4 cycles o ...
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Computers
A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as programs. These programs enable computers to perform a wide range of tasks. A computer system is a nominally complete computer that includes the hardware, operating system (main software), and peripheral equipment needed and used for full operation. This term may also refer to a group of computers that are linked and function together, such as a computer network or computer cluster. A broad range of industrial and consumer products use computers as control systems. Simple special-purpose devices like microwave ovens and remote controls are included, as are factory devices like industrial robots and computer-aided design, as well as general-purpose devices like personal computers and mobile devices like smartphones. Computers power the Internet, which links bill ...
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Memory
Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remembered, it would be impossible for language, relationships, or personal identity to develop. Memory loss is usually described as forgetfulness or amnesia. Memory is often understood as an informational processing system with explicit and implicit functioning that is made up of a sensory processor, short-term (or working) memory, and long-term memory. This can be related to the neuron. The sensory processor allows information from the outside world to be sensed in the form of chemical and physical stimuli and attended to various levels of focus and intent. Working memory serves as an encoding and retrieval processor. Information in the form of stimuli is encoded in accordance with explicit or implicit functions by the working memory processor. ...
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Cache (computing)
In computing, a cache ( ) is a hardware or software component that stores data so that future requests for that data can be served faster; the data stored in a cache might be the result of an earlier computation or a copy of data stored elsewhere. A ''cache hit'' occurs when the requested data can be found in a cache, while a ''cache miss'' occurs when it cannot. Cache hits are served by reading data from the cache, which is faster than recomputing a result or reading from a slower data store; thus, the more requests that can be served from the cache, the faster the system performs. To be cost-effective and to enable efficient use of data, caches must be relatively small. Nevertheless, caches have proven themselves in many areas of computing, because typical computer applications access data with a high degree of locality of reference. Such access patterns exhibit temporal locality, where data is requested that has been recently requested already, and spatial locality, where d ...
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Cache Coherent System
In computer architecture, cache coherence is the uniformity of shared resource data that ends up stored in multiple local caches. When clients in a system maintain caches of a common memory resource, problems may arise with incoherent data, which is particularly the case with CPUs in a multiprocessing system. In the illustration on the right, consider both the clients have a cached copy of a particular memory block from a previous read. Suppose the client on the bottom updates/changes that memory block, the client on the top could be left with an invalid cache of memory without any notification of the change. Cache coherence is intended to manage such conflicts by maintaining a coherent view of the data values in multiple caches. Overview In a shared memory multiprocessor system with a separate cache memory for each processor, it is possible to have many copies of shared data: one copy in the main memory and one in the local cache of each processor that requested it. When one ...
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Ulrich Drepper
Ulrich (), is a German given name, derived from Old High German ''Uodalrich'', ''Odalric''. It is composed of the elements '' uodal-'' meaning "(noble) heritage" and ''-rich'' meaning "rich, powerful". Attested from the 8th century as the name of Alamannic nobility, the name is popularly given from the high medieval period in reference to Saint Ulrich of Augsburg (canonized 993). There is also a surname Ulrich. It is most prevalent in Germany and has the highest density in SwitzerlandThis last name was found in the United States around the year 1840Most Americans with the last name were concentrated in Pennsylvania, which was home to many Pennsylvania Dutch, German immigrant communities. Nowadays in the United States, the name is distributed largely in the Pennsylvania-Ohio regio History Documents record the Old High German name ''Oadalrich'' or ''Uodalrich'' from the later 8th century in Alamannia. The related name ''Adalric'' (Anglo-Saxon cognate '' Æthelric'') is attested fro ...
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