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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 (computing), bus between all the nodes as a "shared bus" (a.k.a. system bus). Directory-based coherence uses a special Directory (computing), 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 a tool to facilitate the communication between different Node (networking), 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 memory, cache blocks, the status of each block includes in which cache coherence "State (computer science), state" that block is, and which nodes are sharing that block at that time, whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cache Coherence
In computer architecture, cache coherence is the uniformity of shared resource data that is stored in multiple local caches. In a cache coherent system, if multiple clients have a cached copy of the same region of a shared memory resource, all copies are the same. Without cache coherence, a change made to the region by one client may not be seen by others, and errors can result when the data used by different clients is mismatched. A cache coherence protocol is used to maintain cache coherency. The two main types are snooping and directory-based protocols. Cache coherence is of particular relevance in multiprocessing systems, where each CPU may have its own local cache of a shared memory resource. 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 of the copies of data is c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiprocessor System-on-chip
A system on a chip (SoC) is an integrated circuit that combines most or all key components of a computer or electronic system onto a single microchip. Typically, an SoC includes a central processing unit (CPU) with memory, input/output, and data storage control functions, along with optional features like a graphics processing unit (GPU), Wi-Fi connectivity, and radio frequency processing. This high level of integration minimizes the need for separate, discrete components, thereby enhancing power efficiency and simplifying device design. High-performance SoCs are often paired with dedicated memory, such as LPDDR, and flash storage chips, such as eUFS or eMMC, which may be stacked directly on top of the SoC in a package-on-package (PoP) configuration or placed nearby on the motherboard. Some SoCs also operate alongside specialized chips, such as cellular modems. Fundamentally, SoCs integrate one or more processor cores with critical peripherals. This comprehensive integrat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coherence Protocol
In computer architecture, cache coherence is the uniformity of shared resource data that is stored in multiple local caches. In a cache coherent system, if multiple clients have a cached copy of the same region of a shared memory resource, all copies are the same. Without cache coherence, a change made to the region by one client may not be seen by others, and errors can result when the data used by different clients is mismatched. A cache coherence protocol is used to maintain cache coherency. The two main types are snooping and directory-based protocols. Cache coherence is of particular relevance in multiprocessing systems, where each CPU may have its own local cache of a shared memory resource. 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 of the copies of data is ch ... [...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, 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 ... [...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, leading to unexpected or inconsistent results. 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 or multithreaded or distributed software programs. Using mutual exclusion can prevent race conditions in distributed software systems. 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 change at slightly different times in response to a change in the source signal. The output may, for a brief period, 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 ''State (computer science), states'' at any given time. The FSM can change from one state to another in response to some Input (computer science), 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 automaton, deterministic finite-state machines and Nondeterministic finite automaton, non-deterministic finite-state machines. For any non-deterministic finite-state machine, an equivalent deterministic one can be constructed. The behavior of state machines can be observed in many devices in modern society that perform a predetermined sequence of actions d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Message Passing Interface
The Message Passing Interface (MPI) is a portable message-passing standard designed to function on parallel computing architectures. The MPI standard defines the syntax and semantics of library routines that are useful to a wide range of users writing portable message-passing programs in C, C++, and Fortran. There are several open-source MPI implementations, which fostered the development of a parallel software industry, and encouraged development of portable and scalable large-scale parallel applications. History The message passing interface effort began in the summer of 1991 when a small group of researchers started discussions at a mountain retreat in Austria. Out of that discussion came a Workshop on Standards for Message Passing in a Distributed Memory Environment, held on April 29–30, 1992 in Williamsburg, Virginia. Attendees at Williamsburg discussed the basic features essential to a standard message-passing interface and established a working group to continu ... [...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] |
Snoopy Cache
Snoopy is an anthropomorphic beagle in the comic strip ''Peanuts'' by American cartoonist Charles M. Schulz. He also appears 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 II). Snoopy can be selfish, gluttonous, and lazy at times, and occasionally mocks his owner, Charlie Brown. But on the w ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
