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Directory-based Coherence
Directory-based coherence is a mechanism to handle Cache coherence problem in Distributed shared memory (DSM) a.k.a. Non-Uniform Memory Access (NUMA). Another popular way is to use a special type of computer bus between all the nodes as a "shared bus" (a.k.a. System bus). Directory-based coherence uses a special directory to serve instead of the shared bus in the bus-based coherence protocols. Both of these designs use the corresponding medium (i.e. directory or bus) as tool to facilitate the communication between different nodes, and to guarantee that the coherence protocol is working properly along all the communicating nodes. In directory based cache coherence, this is done by using this directory to keep track of the status of all cache blocks, the status of each block includes in which cache coherence "state" that block is, and which nodes are sharing that block at that time, which can be used to eliminate the need to broadcast all the signals to all nodes, and only send it to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cache Coherence
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 on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiprocessor System-on-chip
A multiprocessor system on a chip (, ' or ) is a system on a chip (SoC) which includes multiple microprocessors. As such, it is a multi-core system on a chip. MPSoCs are usually targeted for embedded applications. It is used by platforms that contain multiple, usually heterogeneous, processing elements with specific functionalities reflecting the need of the expected application domain, a memory hierarchy and I/O components. All these components are linked to each other by an on-chip interconnect, such as buses and Networks on chip (NoCs). These architectures meet the performance needs of multimedia applications, telecommunication architectures, network security and other application domains while limiting the power consumption through the use of specialised processing elements and architecture. Structure A multiprocessor system on a chip must by definition have multiple processor cores. MPSoCs often contain multiple logically distinct processor modules as well. Addition ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Scalable Coherent Interface
The Scalable Coherent Interface or Scalable Coherent Interconnect (SCI), is a high-speed interconnect standard for shared memory multiprocessing and message passing. The goal was to scale well, provide system-wide memory coherence and a simple interface; i.e. a standard to replace existing buses in multiprocessor systems with one with no inherent scalability and performance limitations. The IEEE Std 1596-1992, IEEE Standard for Scalable Coherent Interface (SCI) was approved by the IEEE standards board on March 19, 1992. It saw some use during the 1990s, but never became widely used and has been replaced by other systems from the early 2000s. History Soon after the Fastbus (IEEE 960) follow-on Futurebus (IEEE 896) project in 1987, some engineers predicted it would already be too slow for the high performance computing marketplace by the time it would be released in the early 1990s. In response, a "Superbus" study group was formed in November 1987. Another working group of the sta ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Race Condition
A race condition or race hazard is the condition of an electronics, software, or other system where the system's substantive behavior is dependent on the sequence or timing of other uncontrollable events. It becomes a bug when one or more of the possible behaviors is undesirable. The term ''race condition'' was already in use by 1954, for example in David A. Huffman's doctoral thesis "The synthesis of sequential switching circuits". Race conditions can occur especially in logic circuits, multithreaded, or distributed Distribution may refer to: Mathematics *Distribution (mathematics), generalized functions used to formulate solutions of partial differential equations *Probability distribution, the probability of a particular value or value range of a varia ... software programs. In electronics A typical example of a race condition may occur when a logic gate combines signals that have traveled along different paths from the same source. The inputs to the gate can chan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Finite-state Machine
A finite-state machine (FSM) or finite-state automaton (FSA, plural: ''automata''), finite automaton, or simply a state machine, is a mathematical model of computation. It is an abstract machine that can be in exactly one of a finite number of '' states'' at any given time. The FSM can change from one state to another in response to some inputs; the change from one state to another is called a ''transition''. An FSM is defined by a list of its states, its initial state, and the inputs that trigger each transition. Finite-state machines are of two types— deterministic finite-state machines and non-deterministic finite-state machines. A deterministic finite-state machine can be constructed equivalent to any non-deterministic one. The behavior of state machines can be observed in many devices in modern society that perform a predetermined sequence of actions depending on a sequence of events with which they are presented. Simple examples are vending machines, which dispense p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cache Coherence
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 on ... [...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 a lot of bandwidth that is 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 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Directory Protocol State Transtion Diagram
Directory may refer to: * Directory (computing), or folder, a file system structure in which to store computer files * Directory (OpenVMS command) * Directory service, a software application for organizing information about a computer network's users and resources * Directory (political), a system under which a country is ruled by a college of several people who jointly exercise the powers of a head of state or head of government ** French Directory, the government in revolutionary France from 1795 to 1799 * Business directory, a listing of information about suppliers and manufacturers * Telephone directory, a book which allows telephone numbers to be found given the subscriber's name * Web directory, an organized collection of links to websites See also * Director (other) * Directorate (other) Directorate may refer to: Contemporary *Directorates of the Scottish Government * Directorate-General, a type of specialised administrative body in the European Union ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Directory Scheme
Directory may refer to: * Directory (computing), or folder, a file system structure in which to store computer files * Directory (OpenVMS command) * Directory service, a software application for organizing information about a computer network's users and resources * Directory (political), a system under which a country is ruled by a college of several people who jointly exercise the powers of a head of state or head of government ** French Directory, the government in revolutionary France from 1795 to 1799 * Business directory, a listing of information about suppliers and manufacturers * Telephone directory, a book which allows telephone numbers to be found given the subscriber's name * Web directory, an organized collection of links to websites See also * Director (other) * Directorate (other) Directorate may refer to: Contemporary *Directorates of the Scottish Government * Directorate-General, a type of specialised administrative body in the European Union ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Snoopy Cache
Snoopy is an anthropomorphic beagle in the comic strip ''Peanuts'' by Charles M. Schulz. He can also be found in all of the ''Peanuts'' films and television specials. Since his debut on October 4, 1950, Snoopy has become one of the most recognizable and iconic characters in the comic strip and is considered more famous than Charlie Brown in some countries. The original drawings of Snoopy were inspired by Spike, one of Schulz's childhood dogs. Traits Snoopy is a loyal, imaginative, and good-natured beagle who is prone to imagining fantasy lives, including being an author, a college student known as "Joe Cool", an attorney, and a World War I flying ace. He is perhaps best known in this last persona, wearing an aviator's helmet and goggles and a scarf while carrying a swagger stick (like a stereotypical British Army officer of World War I and World War II, II). Snoopy can be selfish, gluttonous and lazy at times, and occasionally mocks his owner, Charlie Brown. But on the whole, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Origin 3000
The Origin 3000 and the Onyx 3000 is a family of mid-range and high-end computers developed and manufactured by SGI. The Origin 3000 is a server, and the Onyx 3000 is a visualization system. Both systems were introduced in July 2000 to succeed the Origin 2000 and the Onyx2 respectively. These systems ran the IRIX 6.5 Advanced Server Environment operating system. Entry-level variants of these systems based on the same architecture but with a different hardware implementation are known as the Origin 300 and Onyx 300. The Origin 3000 was succeeded by the Altix 3000 in 2004 and the last model was discontinued on 29 December 2006, while the Onyx 3000 was succeeded by the Onyx4 and the Itanium-based Prism in 2004 and the last model was discontinued on 25 March 2005. Origin 3000 Models Special * Origin 3200C - This model was a cluster of nodes that consist of entire Origin 3200 systems. This model could scale to thousands of processors. The clustering technology used wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
