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List Of Cache Coherency Protocols
Examples of coherency protocols for cache memory are listed here. For simplicity, all "miss" Read and Write status transactions which obviously come from state "I" (or miss of Tag), in the diagrams are not shown. They are shown directly on the new state. Many of the following protocols have only historical value. At the moment the main protocols used are the R-MESI type / MESIF protocols and the HRT-ST-MESI (MOESI type) or a subset or an extension of these. Cache coherency problem In systems as Multiprocessor system architecture#Symmetric multiprocessor system, Multiprocessor system, Multi-core processor, multi-core and Non-uniform memory access, NUMA system, where a dedicated cache for each ''processor'', ''core'' or ''node'' is used, a consistency problem may occur when a same data is stored in more than one cache. This problem arises when a data is modified in one cache. This problem can be solved in two ways: # Invalidate all the copies on other caches (broadcast-invalida ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiprocessor System Architecture
A multiprocessor (MP) system is defined as "a system with more than one ''Central processing unit, processor''", and, more precisely, "a number of central processing units linked together to enable parallel processing to take place". The key objective of a multiprocessor is to boost a system's execution speed. The other objectives are fault tolerance and application matching. The term "multiprocessor" can be confused with the term "multiprocessing". While multiprocessing is a type of processing in which two or more processors work together to execute multiple programs simultaneously, multiprocessor refers to a hardware architecture that allows multiprocessing. Multiprocessor systems are classified according to how processor memory access is handled and whether system processors are of a single type or various ones. Multiprocessor system types There are many types of multiprocessor systems: * Loosely coupled multiprocessor system * Tightly coupled multiprocessor system * Ho ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Illinois Protocol
The MESI protocol is an invalidate-based cache coherence protocol, and is one of the most common protocols that support write-back caches. It is also known as the Illinois protocol due to its development at the University of Illinois at Urbana-Champaign. Write back caches can save considerable bandwidth generally wasted on a write through cache. There is always a dirty state present in write-back caches that indicates that the data in the cache is different from that in the main memory. The Illinois Protocol requires a cache-to-cache transfer on a miss if the block resides in another cache. This protocol reduces the number of main memory transactions with respect to the MSI protocol. This marks a significant improvement in performance. States The letters in the acronym MESI represent four exclusive states that a cache line can be marked with (encoded using two additional bits): ;Modified (M): The cache line is present only in the current cache, and is ''dirty'' - it has been mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bull HN ISI Protocol
A bull is an intact (i.e., not castrated) adult male of the species ''Bos taurus'' (cattle). More muscular and aggressive than the females of the same species (i.e. cows proper), bulls have long been an important symbol in many religions, including for sacrifices. These animals play a significant role in beef ranching, dairy farming, and a variety of sporting and cultural activities, including bullfighting and bull riding. Due to their temperament, handling of bulls requires precautions. Nomenclature The female counterpart to a bull is a cow, while a male of the species that has been castrated is a ''steer'', '' ox'', or ''bullock'', although in North America, this last term refers to a young bull. Use of these terms varies considerably with area and dialect. Colloquially, people unfamiliar with cattle may also refer to steers and heifers as "cows", and bovines of aggressive or long-horned breeds as "bulls" regardless of sex. A wild, young, unmarked bull is known as a '' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Write-once (or Write-first) Protocol , computer storage that can be written to once, but read from multiple times
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Write once may refer to: * Write once, run anywhere, a slogan for the cross-platform benefits of Java * Write once, compile anywhere, a slogan for the cross-platform benefits of C * Write-once (cache coherency), a write-invalidate protocol in computer memory design * Write once read many Write once read many (WORM) describes a data storage device in which information, once written, cannot be modified. This write protection affords the assurance that the data cannot be tampered with once it is written to the device, excluding the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AMD64
x86-64 (also known as x64, x86_64, AMD64, and Intel 64) is a 64-bit extension of the x86 instruction set. It was announced in 1999 and first available in the AMD Opteron family in 2003. It introduces two new operating modes: 64-bit mode and compatibility mode, along with a new four-level paging mechanism. In 64-bit mode, x86-64 supports significantly larger amounts of virtual memory and physical memory compared to its 32-bit predecessors, allowing programs to utilize more memory for data storage. The architecture expands the number of general-purpose registers from 8 to 16, all fully general-purpose, and extends their width to 64 bits. Floating-point arithmetic is supported through mandatory SSE2 instructions in 64-bit mode. While the older x87 FPU and MMX registers are still available, they are generally superseded by a set of sixteen 128-bit vector registers (XMM registers). Each of these vector registers can store one or two double-precision floating-point numbers, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MOESI Protocol
Modified Owned Exclusive Shared Invalid (MOESI) is a full cache coherency protocol that encompasses all of the possible states commonly used in other protocols. In addition to the four common MESI protocol states, there is a fifth "Owned" state representing data that is both modified and shared. This avoids the need to write modified data back to main memory before sharing it. While the data must still be written back eventually, the write-back may be deferred . In order for this to be possible, direct cache-to-cache transfers of data must be possible, so a cache with the data in the modified state can supply that data to another reader without transferring it to memory. As discussed in AMD64 Architecture Programmer's Manual Vol. 2 ''System Programming'', each cache line is in one of five states: ;Modified: This cache has the only valid copy of the cache line, and has made changes to that copy. The cached copy may be further modified freely. ;Owned: This line is one of seve ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Berkeley Protocol
Berkeley most often refers to: *Berkeley, California, a city in the United States **University of California, Berkeley, a public university in Berkeley, California *George Berkeley (1685–1753), Anglo-Irish philosopher Berkeley may also refer to: Places Australia * Berkeley, New South Wales, a suburb of Wollongong Canada * Berkeley, Ontario, a community in Grey County United Kingdom * Berkeley (hundred), an administrative division from late Saxon period to the 19th century * Berkeley, Gloucestershire, a town in England United States * Berkeley, California, a city in the San Francisco Bay Area, the largest city named Berkeley * Berkeley, Denver, a neighborhood in Denver, Colorado * Berkeley, Illinois, a suburb of Chicago * Berkeley, Missouri, a northwestern suburb of St. Louis * Berkeley Township, Ocean County, New Jersey * Berkeley, Rhode Island * Berkeley, Virginia (other) * Berkeley, West Virginia * Berkeley County (other) People * Berkeley (given nam ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MESI Protocol
The MESI protocol is an invalidate-based cache coherence protocol, and is one of the most common protocols that support write-back caches. It is also known as the Illinois protocol due to its development at the University of Illinois at Urbana-Champaign. Write back caches can save considerable bandwidth generally wasted on a write through cache. There is always a dirty state present in write-back caches that indicates that the data in the cache is different from that in the main memory. The Illinois Protocol requires a cache-to-cache transfer on a miss if the block resides in another cache. This protocol reduces the number of main memory transactions with respect to the MSI protocol. This marks a significant improvement in performance. States The letters in the acronym MESI represent four exclusive states that a cache line can be marked with (encoded using two additional bits): ;Modified (M): The cache line is present only in the current cache, and is ''dirty'' - it has been m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Firefly (DEC) Protocol
The Lampyridae are a family of elateroid beetles with more than 2,000 described species, many of which are light-emitting. They are soft-bodied beetles commonly called fireflies, lightning bugs, or glowworms for their conspicuous production of light, mainly during twilight, to attract mates. The type species is ''Lampyris noctiluca'', the common glow-worm of Europe. Light production in the Lampyridae is thought to have originated as a warning signal that the larvae were distasteful. This ability to create light was then co-opted as a mating signal and, in a further development, adult female fireflies of the genus ''Photuris'' mimic the flash pattern of the ''Photinus'' beetle to trap their males as prey. Fireflies are found in temperate and tropical climates. Many live in marshes or in wet, wooded areas where their larvae have abundant sources of food. Although all known fireflies glow as larvae, only some species produce light in their adult stage, and the location of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PowerPC 7xx
The PowerPC 7xx is a family of third generation 32-bit PowerPC microprocessors designed and manufactured by IBM and Motorola (spun off as Freescale Semiconductor bought by NXP Semiconductors). This family is called the PowerPC G3 by Apple Computer (later Apple Inc.), which introduced it on November 10, 1997. A number of microprocessors from different vendors have been used under the "PowerPC G3" name. Such designations were applied to Mac computers such as the PowerBook G3, the multicolored iMacs, iBooks and several desktops, including both the Beige and Blue and White Power Macintosh G3s. The low power requirements and small size made the processors ideal for laptops and the name lived out its last days at Apple in the iBook. The 7xx family is also widely used in embedded devices like printers, routers, storage devices, spacecraft, and video game consoles. The 7xx family had its shortcomings, namely lack of SMP support and SIMD capabilities and a relatively weak FPU. Mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Synapse Protocol
In the nervous system, a synapse is a structure that allows a neuron (or nerve cell) to pass an electrical or chemical signal to another neuron or a target effector cell. Synapses can be classified as either chemical or electrical, depending on the mechanism of signal transmission between neurons. In the case of electrical synapses, neurons are coupled bidirectionally with each other through gap junctions and have a connected cytoplasmic milieu. These types of synapses are known to produce synchronous network activity in the brain, but can also result in complicated, chaotic network level dynamics. Therefore, signal directionality cannot always be defined across electrical synapses. Chemical synapses, on the other hand, communicate through neurotransmitters released from the presynaptic neuron into the synaptic cleft. Upon release, these neurotransmitters bind to specific receptors on the postsynaptic membrane, inducing an electrical or chemical response in the target neuron. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
