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49-413: SHARC processors are typically intended to have a good number of serial links to other SHARC processors nearby, to be used as a low-cost alternative to SMP . The SHARC is a Harvard architecture word-addressed VLIW processor; it knows nothing of 8-bit or 16-bit values since each address is used to point to a whole 32-bit word, not just an octet . It is thus neither little-endian nor big-endian, though

98-429: A multiprocessor computer hardware and software architecture where two or more identical processors are connected to a single, shared main memory , have full access to all input and output devices, and are controlled by a single operating system instance that treats all processors equally, reserving none for special purposes. Most multiprocessor systems today use an SMP architecture. In the case of multi-core processors ,

147-432: A NUMA architecture, processors may access local memory quickly and remote memory more slowly. This can dramatically improve memory throughput as long as the data are localized to specific processes (and thus processors). On the downside, NUMA makes the cost of moving data from one processor to another, as in workload balancing, more expensive. The benefits of NUMA are limited to particular workloads, notably on servers where

196-433: A compiler may use either convention if it implements 64-bit data and/or some way to pack multiple 8-bit or 16-bit values into a single 32-bit word. In C, the characters are 32-bit as they are the smallest addressable words by standard. The word size is 48-bit for instructions, 32-bit for integers and normal floating-point, and 40-bit for extended floating-point. Code and data are normally fetched from on-chip memory, which

245-514: A few limits on the scalability of SMP due to cache coherence and shared objects. Uniprocessor and SMP systems require different programming methods to achieve maximum performance. Programs running on SMP systems may experience an increase in performance even when they have been written for uniprocessor systems. This is because hardware interrupts usually suspends program execution while the kernel that handles them can execute on an idle processor instead. The effect in most applications (e.g. games)

294-466: A high speed communication system ( Gigabit Ethernet is common). A Linux Beowulf cluster is an example of a loosely coupled system. Tightly coupled systems perform better and are physically smaller than loosely coupled systems, but have historically required greater initial investments and may depreciate rapidly; nodes in a loosely coupled system are usually inexpensive commodity computers and can be recycled as independent machines upon retirement from

343-532: A master/slave multiprocessor system of microprocessors is the Tandy/Radio Shack TRS-80 Model 16 desktop computer which came out in February 1982 and ran the multi-user/multi-tasking Xenix operating system, Microsoft's version of UNIX (called TRS-XENIX). The Model 16 has two microprocessors: an 8-bit Zilog Z80 CPU running at 4 MHz, and a 16-bit Motorola 68000 CPU running at 6 MHz. When

392-474: A number of ways, including asymmetric multiprocessing (ASMP), non-uniform memory access (NUMA) multiprocessing, and clustered multiprocessing. In a master/slave multiprocessor system, the master CPU is in control of the computer and the slave CPU(s) performs assigned tasks. The CPUs can be completely different in terms of speed and architecture. Some (or all) of the CPUs can share a common bus, each can also have

441-580: A pool of homogeneous processors running independently of each other. Each processor, executing different programs and working on different sets of data, has the capability of sharing common resources (memory, I/O device, interrupt system and so on) that are connected using a system bus or a crossbar . SMP systems have centralized shared memory called main memory (MM) operating under a single operating system with two or more homogeneous processors. Usually each processor has an associated private high-speed memory known as cache memory (or cache) to speed up

490-528: A private bus (for private resources), or they may be isolated except for a common communications pathway. Likewise, the CPUs can share common RAM and/or have private RAM that the other processor(s) cannot access. The roles of master and slave can change from one CPU to another. Two early examples of a mainframe master/slave multiprocessor are the Bull Gamma 60 and the Burroughs B5000 . An early example of

539-571: A quad-core device, called the Companion core, built specifically for executing tasks at a lower frequency during mobile active standby mode, video playback, and music playback. Project Kal-El ( Tegra 3 ), patented by NVIDIA, was the first SoC (System on Chip) to implement this new vSMP technology. This technology not only reduces mobile power consumption during active standby state, but also maximizes quad core performance during active usage for intensive mobile applications. Overall this technology addresses

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588-459: A small write-through cache connected to a common memory to form a shared memory system. Another early commercial Unix SMP implementation was the NUMA based Honeywell Information Systems Italy XPS-100 designed by Dan Gielan of VAST Corporation in 1985. Its design supported up to 14 processors, but due to electrical limitations, the largest marketed version was a dual processor system. The operating system

637-640: A special 48-bit register is provided for this purpose. The special 48-bit register may be accessed as a pair of smaller registers, allowing movement to and from the normal registers. Off-chip memory can be used with the SHARC. This memory can only be configured for one single size. If the off-chip memory is configured as 32-bit words to avoid waste, then only the on-chip memory may be used for code execution and extended floating-point. Operating systems may use overlays to work around this problem, transferring 48-bit data to on-chip memory as needed for execution. A DMA engine

686-678: A system with more than one process running can run different processes on different processors. On personal computers , SMP is less useful for applications that have not been modified. If the system rarely runs more than one process at a time, SMP is useful only for applications that have been modified for multithreaded (multitasked) processing. Custom-programmed software can be written or modified to use multiple threads, so that it can make use of multiple processors. Multithreaded programs can also be used in time-sharing and server systems that support multithreading, allowing them to make more use of multiple processors. In current SMP systems, all of

735-409: A uniprocessor system, because different programs can run on different CPUs simultaneously. Conversely, asymmetric multiprocessing (AMP) usually allows only one processor to run a program or task at a time. For example, AMP can be used in assigning specific tasks to CPU based to priority and importance of task completion. AMP was created well before SMP in terms of handling multiple CPUs, which explains

784-436: A uniprocessor system. SMP systems can also lead to more complexity regarding instruction sets. A homogeneous processor system typically requires extra registers for "special instructions" such as SIMD (MMX, SSE, etc.), while a heterogeneous system can implement different types of hardware for different instructions/uses. When more than one program executes at the same time, an SMP system has considerably better performance than

833-399: Is generally used to denote that scenario. Other authors prefer to refer to the operating system techniques as multiprogramming and reserve the term multiprocessing for the hardware aspect of having more than one processor. The remainder of this article discusses multiprocessing only in this hardware sense. In Flynn's taxonomy , multiprocessors as defined above are MIMD machines. As

882-399: Is handled independently, this creates an embarrassingly parallel situation across the entire multi-compilation-unit project, allowing near linear scaling of compilation time. Distributed computing projects are inherently parallel by design.) Systems programmers must build support for SMP into the operating system , otherwise, the additional processors remain idle and the system functions as

931-407: Is intended by SMP is a shared memory multiprocessor where the cost of accessing a memory location is the same for all processors; that is, it has uniform access costs when the access actually is to memory. If the location is cached, the access will be faster, but cache access times and memory access times are the same on all processors." SMP systems are tightly coupled multiprocessor systems with

980-411: Is not so much a performance increase as the appearance that the program is running much more smoothly. Some applications, particularly building software and some distributed computing projects, run faster by a factor of (nearly) the number of additional processors. (Compilers by themselves are single threaded, but, when building a software project with multiple compilation units, if each compilation unit

1029-478: Is provided for this. True paging is impossible without an external MMU . The SHARC has a 32-bit word-addressed address space. Depending on word size this is 16 GB, 20 GB, or 24 GB (using the common definition of an 8-bit "byte"). SHARC instructions may contain a 32-bit immediate operand. Instructions without this operand are generally able to perform two or more operations simultaneously. Many instructions are conditional, and may be preceded with "if condition " in

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1078-503: Is serialized; this and cache coherency issues cause performance to lag slightly behind the number of additional processors in the system. SMP uses a single shared system bus that represents one of the earliest styles of multiprocessor machine architectures, typically used for building smaller computers with up to 8 processors. Larger computer systems might use newer architectures such as NUMA (Non-Uniform Memory Access), which dedicates different memory banks to different processors. In

1127-411: Is sometimes contrasted with multitasking , which may use just a single processor but switch it in time slices between tasks (i.e. a time-sharing system ). Multiprocessing however means true parallel execution of multiple processes using more than one processor. Multiprocessing doesn't necessarily mean that a single process or task uses more than one processor simultaneously; the term parallel processing

1176-753: The Michigan Terminal System (MTS), used both CPUs. Both processors could access data channels and initiate I/O. In OS/360 M65MP, peripherals could generally be attached to either processor since the operating system kernel ran on both processors (though with a "big lock" around the I/O handler). The MTS supervisor (UMMPS) has the ability to run on both CPUs of the IBM System/360 model 67–2. Supervisor locks were small and used to protect individual common data structures that might be accessed simultaneously from either CPU. Other mainframes that supported SMP included

1225-554: The UNIVAC 1108 II , released in 1965, which supported up to three CPUs, and the GE-635 and GE-645 , although GECOS on multiprocessor GE-635 systems ran in a master-slave asymmetric fashion, unlike Multics on multiprocessor GE-645 systems, which ran in a symmetric fashion. Starting with its version 7.0 (1972), Digital Equipment Corporation 's operating system TOPS-10 implemented the SMP feature,

1274-739: The assembly language . There are a number of condition choices, similar to the choices provided by the x86 flags register. There are two delay slots . After a jump, two instructions following the jump will normally be executed. The SHARC processor has built-in support for loop control. Up to 6 levels may be used, avoiding the need for normal branching instructions and the normal bookkeeping related to loop exit. The SHARC has two full sets of general-purpose registers. Code can instantly switch between them, allowing for fast context switches between an application and an OS or between two threads. Symmetric multiprocessing Symmetric multiprocessing or shared-memory multiprocessing ( SMP ) involves

1323-461: The 68000 CPU. The Z-80 can be used to do other tasks. The earlier TRS-80 Model II , which was released in 1979, could also be considered a multiprocessor system as it had both a Z-80 CPU and an Intel 8021 microcontroller in the keyboard. The 8021 made the Model II the first desktop computer system with a separate detachable lightweight keyboard connected with by a single thin flexible wire, and likely

1372-402: The SMP architecture applies to the cores, treating them as separate processors. Professor John D. Kubiatowicz considers traditionally SMP systems to contain processors without caches. Culler and Pal-Singh in their 1998 book "Parallel Computer Architecture: A Hardware/Software Approach" mention: "The term SMP is widely used but causes a bit of confusion. [...] The more precise description of what

1421-656: The Xeon processors via a common pipe and the Opteron processors via independent pathways to the system RAM . Chip multiprocessors, also known as multi-core computing, involves more than one processor placed on a single chip and can be thought of the most extreme form of tightly coupled multiprocessing. Mainframe systems with multiple processors are often tightly coupled. Loosely coupled multiprocessor systems (often referred to as clusters ) are based on multiple standalone relatively low processor count commodity computers interconnected via

1470-511: The bus level. These CPUs may have access to a central shared memory (SMP or UMA ), or may participate in a memory hierarchy with both local and shared memory (SM)( NUMA ). The IBM p690 Regatta is an example of a high end SMP system. Intel Xeon processors dominated the multiprocessor market for business PCs and were the only major x86 option until the release of AMD 's Opteron range of processors in 2004. Both ranges of processors had their own onboard cache but provided access to shared memory;

1519-451: The cluster. Power consumption is also a consideration. Tightly coupled systems tend to be much more energy-efficient than clusters. This is because a considerable reduction in power consumption can be realized by designing components to work together from the beginning in tightly coupled systems, whereas loosely coupled systems use components that were not necessarily intended specifically for use in such systems. Loosely coupled systems have

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1568-441: The data are often associated strongly with certain tasks or users. Finally, there is computer clustered multiprocessing (such as Beowulf ), in which not all memory is available to all processors. Clustering techniques are used fairly extensively to build very large supercomputers. Variable Symmetric Multiprocessing (vSMP) is a specific mobile use case technology initiated by NVIDIA. This technology includes an extra fifth core in

1617-488: The data for that task is located in memory, provided that each task in the system is not in execution on two or more processors at the same time. With proper operating system support, SMP systems can easily move tasks between processors to balance the workload efficiently. The earliest production system with multiple identical processors was the Burroughs B5000 , which was functional around 1961. However at run-time this

1666-518: The definition of multiprocessing can vary with context, mostly as a function of how CPUs are defined ( multiple cores on one die , multiple dies in one package , multiple packages in one system unit , etc.). According to some on-line dictionaries, a multiprocessor is a computer system having two or more processing units (multiple processors) each sharing main memory and peripherals, in order to simultaneously process programs. A 2009 textbook defined multiprocessor system similarly, but noting that

1715-712: The earliest system running SMP was the DECSystem 1077 dual KI10 processor system. Later KL10 system could aggregate up to 8 CPUs in a SMP manner. In contrast, DECs first multi-processor VAX system, the VAX-11/782, was asymmetric, but later VAX multiprocessor systems were SMP. Early commercial Unix SMP implementations included the Sequent Computer Systems Balance 8000 (released in 1984) and Balance 21000 (released in 1986). Both models were based on 10 MHz National Semiconductor NS32032 processors, each with

1764-741: The first keyboard to use a dedicated microcontroller, both attributes that would later be copied years later by Apple and IBM. In multiprocessing, the processors can be used to execute a single sequence of instructions in multiple contexts ( single instruction, multiple data or SIMD, often used in vector processing ), multiple sequences of instructions in a single context ( multiple instruction, single data or MISD, used for redundancy in fail-safe systems and sometimes applied to describe pipelined processors or hyper-threading ), or multiple sequences of instructions in multiple contexts ( multiple instruction, multiple data or MIMD). Tightly coupled multiprocessor systems contain multiple CPUs that are connected at

1813-510: The lack of performance based on the example provided. In cases where an SMP environment processes many jobs, administrators often experience a loss of hardware efficiency. Software programs have been developed to schedule jobs and other functions of the computer so that the processor utilization reaches its maximum potential. Good software packages can achieve this maximum potential by scheduling each CPU separately, as well as being able to integrate multiple SMP machines and clusters. Access to RAM

1862-473: The main memory data access and to reduce the system bus traffic. Processors may be interconnected using buses, crossbar switches or on-chip mesh networks. The bottleneck in the scalability of SMP using buses or crossbar switches is the bandwidth and power consumption of the interconnect among the various processors, the memory, and the disk arrays. Mesh architectures avoid these bottlenecks, and provide nearly linear scalability to much higher processor counts at

1911-556: The need for increase in battery life performance during active and standby usage by reducing the power consumption in mobile processors. Unlike current SMP architectures, the vSMP Companion core is OS transparent meaning that the operating system and the running applications are totally unaware of this extra core but are still able to take advantage of it. Some of the advantages of the vSMP architecture includes cache coherency, OS efficiency, and power optimization. The advantages for this architecture are explained below: These advantages lead

1960-615: The processors are tightly coupled inside the same box with a bus or switch; on earlier SMP systems, a single CPU took an entire cabinet. Some of the components that are shared are global memory, disks, and I/O devices. Only one copy of an OS runs on all the processors, and the OS must be designed to take advantage of this architecture. Some of the basic advantages involves cost-effective ways to increase throughput. To solve different problems and tasks, SMP applies multiple processors to that one problem, known as parallel programming . However, there are

2009-441: The processors may share "some or all of the system’s memory and I/O facilities"; it also gave tightly coupled system as a synonymous term. At the operating system level, multiprocessing is sometimes used to refer to the execution of multiple concurrent processes in a system, with each process running on a separate CPU or core, as opposed to a single process at any one instant. When used with this definition, multiprocessing

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2058-479: The sacrifice of programmability: Serious programming challenges remain with this kind of architecture because it requires two distinct modes of programming; one for the CPUs themselves and one for the interconnect between the CPUs. A single programming language would have to be able to not only partition the workload, but also comprehend the memory locality, which is severe in a mesh-based architecture. SMP systems allow any processor to work on any task no matter where

2107-739: The symmetry (or lack thereof) in a given system. For example, hardware or software considerations may require that only one particular CPU respond to all hardware interrupts, whereas all other work in the system may be distributed equally among CPUs; or execution of kernel-mode code may be restricted to only one particular CPU, whereas user-mode code may be executed in any combination of processors. Multiprocessing systems are often easier to design if such restrictions are imposed, but they tend to be less efficient than systems in which all CPUs are utilized. Systems that treat all CPUs equally are called symmetric multiprocessing (SMP) systems. In systems where all CPUs are not equal, system resources may be divided in

2156-494: The system is booted, the Z-80 is the master and the Xenix boot process initializes the slave 68000, and then transfers control to the 68000, whereupon the CPUs change roles and the Z-80 becomes a slave processor responsible for all I/O operations including disk, communications, printer and network, as well as the keyboard and integrated monitor, while the operating system and applications run on

2205-420: The term "multiprocessor" normally refers to tightly coupled systems in which all processors share memory, multiprocessors are not the entire class of MIMD machines, which also contains message passing multicomputer systems. In a multiprocessing system, all CPUs may be equal, or some may be reserved for special purposes. A combination of hardware and operating system software design considerations determine

2254-404: The user must split into regions of different word sizes as desired. Small data types may be stored in wider memory, simply wasting the extra space. A system that does not use 40-bit extended floating-point might divide the on-chip memory into two sections, a 48-bit one for code and a 32-bit one for everything else. Most memory-related CPU instructions can not access all the bits of 48-bit memory, but

2303-458: The vSMP architecture to considerably benefit over other architectures using asynchronous clocking technologies. Multiprocessing#Processor coupling Multiprocessing is the use of two or more central processing units (CPUs) within a single computer system . The term also refers to the ability of a system to support more than one processor or the ability to allocate tasks between them. There are many variations on this basic theme, and

2352-477: Was asymmetric , with one processor restricted to application programs while the other processor mainly handled the operating system and hardware interrupts. The Burroughs D825 first implemented SMP in 1962. IBM offered dual-processor computer systems based on its System/360 Model 65 and the closely related Model 67 and 67–2. The operating systems that ran on these machines were OS/360 M65MP and TSS/360 . Other software developed at universities, notably

2401-522: Was derived and ported by VAST Corporation from AT&T 3B20 Unix SysVr3 code used internally within AT&;T. Earlier non-commercial multiprocessing UNIX ports existed, including a port named MUNIX created at the Naval Postgraduate School by 1975. Time-sharing and server systems can often use SMP without changes to applications, as they may have multiple processes running in parallel, and

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