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Computer Architecture Articles
Page 18 of 26
What is COMA?
COMA stands for Cache-only memory access machines. A COMA machine includes several processing nodes connected by an interconnection network. Each processing node has a high-implementation processor, a cache, and an allocation of the global shared memory.COMA machines try to avoid the problems of static memory allocation of NUMA and CC-NUMA machines by excluding main memory blocks from the local memory of nodes and employing only large caches as node memories. In these architectures only cache memories are present; no main memory is employed either in the form of a central shared memory as in UMA machines or the form of ...
Read MoreWhat is CC-NUMA?
CC-NUMA stands for Cache-coherent non-uniform memory access machines. A CC-NUMA machine includes several processing nodes linked through a high-bandwidth low-latency interconnection network. Each processing node includes a high-implementation processor, the related cache, and an allocation of the global shared memory.Cache coherence is preserved by a directory-based, write-invalidate cache coherence protocol. It can maintain all caches consistent, every processing node has a directory memory corresponding to its allocation of the shared physical memory.For each memory line, the directory memory saves recognizes remote nodes caching that line. Thus, utilizing the directory, it is applicable for a node writing a location to send ...
Read MoreWhat is Cray T3D?
Cray T3D is the most recent NUMA machine that was designed to provide a highly scalable parallel supercomputer that can incorporate both the shared memory and the message-passing programming paradigms. As in other NUMA machines, the shared memory is distributed among the processing elements to avoid the memory access bottleneck and there is no hardware support for cache coherency. However, a special software package and programming model, called the CRAFT, manages coherence and guarantees the integrity of the data.The Cray T3D hardware structure is divided into three parts are as follows −MicroarchitectureMacroarchitectureThe microarchitecture is based on Digital’s 21064 Alpha AXP ...
Read MoreWhat is Hector in Computer Architecture?
Hector is a hierarchical NUMA machine consisting of stations connected by a hierarchy of ring networks. Stations are symmetric multiprocessors where the processing modules are linked by an individual bus. Nodes comprise three main units − a processor/cache unit, a memory unit, and the station bus interface which connects the otherwise separated processor and memory buses.The separation of two bus enables other processors to access this memory while the processor performs memory access operations in off-node memory. The processing modules of the machine are grouped into shared bus symmetric multiprocessors, called stations. These are connected by bit-parallel local rings, which ...
Read MoreWhat is UMA?
UMA represents Uniform memory access. It is a shared memory architecture used in parallel computers. All the processors in the UMA model share the physical memory uniformly. In UMA architecture, access time to a memory location is autonomous of which processor creates the request or which memory chip includes the shared data.Although the UMA architecture is not suitable for building scalable parallel computers, it is excellent for constructing small-size single bus multiprocessors. Two such machines are the Encore Multimax of Encore Computer Corporation representing the technology of the late 1980s and the Power Challenge of Silicon Graphics Computing Systems representing ...
Read MoreWhat is Deterministic Routing?
In deterministic routing, the path is fully determined by the source and destination nodes. Intermediate nodes are unable to direct messages even in the case of network congestion.Deterministic routing can be further classified according to the node position where the deterministic path is selected. In source routing, it is the source node that selects the complete path between the source and destination nodes. Distributed routing gives each intermediate node the freedom to independently determine the next node of the path to which the message should be sent. There are three deterministic routing schemes are as follows −Street-sign routing − Street-sign ...
Read MoreWhat is the design space of switching techniques?
Switching is the actual mechanism by which a message is removed from the input buffer and placed in the output buffer. The switching technique applied has an over-whelming effect on message latency and hence the choice of switching method is crucial in designing any distributed memory computer. The design space of the switching technique is shown in the figure.Packet Switching (store and forward)In the first-generation multicomputer, the packet switching mechanism was borrowed from the world of computer networks. The packet switching mechanism behaves in a store and forward manner similar to the mail service. A message is divided into packets ...
Read MoreWhat is design space of static interconnection topology?
In a static network, the connection between input and output nodes is fixed and cannot be modified. Static interconnection network cannot be reconfigured. Examples of this network are linear array, ring, chordal ring, tree, star, fat tree, mesh, tours, systolic arrays, and hypercube. The design space for static interconnection topologies is shown in the figure.Linear ArrayThis is a most elementary interconnection design. In this processors are linked in a linear one-dimensional array. The first and last processors are linked with one adjacent processor and the middle processing components are linked with two adjacent processors. It is a one-dimensional interconnection network.RingThis ...
Read MoreWhat are Direct Interconnection Networks?
Direct Interconnection networks are used to connect different processing elements or different process memory. Interconnection networks are also known as multi-stage interconnection networks (or MINs), are high-speed computer networks.Characteristics of Direct Interconnection NetworkTopology − It denotes how the nodes of a network are organized.Network Diameter − It is the minimum distance between the most distant nodes in a network. The distance is measured in terms of the multiple specific hops between any two nodes.Node degree − The number of edges linked with a node is known as node degree. If the edge carries information from the node, it is known ...
Read MoreWhat is Distributed memory MIMD Architecture?
Distributed memory MIMD Architecture is known as Multicomputer. It can replicate the processor/memory pairs and link them through an interconnection network. The processor/memory pair is known as the processing element (PE) and PEs work more or less separated from each other.Whenever interaction between them is possible through message passing one PEs cannot directly access the memory of other PE. This class of MIMD machines is known as distributed memory MIMD architectures or message passing MIMD architectures.In distributed-memory MIMD machines, each processor has its memory location. Each processor has no explicit knowledge about other processor's memory. For data to be transmitted, ...
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