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本文是一篇留学生的Internet essay 范文：“Computer System Architecture of Buses-公共汽车的计算机系统架构”，本报告重点介绍公交车的计算机系统架构。该研究基于AMD K计算机系统所使用的公共汽车的。在公交特性方面，我们已经涵盖了公交宽度和公交速度，公交类型和公交线路，以及“公交”对“网络”的优缺点。这些包括公共汽车的特性、公共汽车的仲裁和公共汽车的拓扑。
Abstract This report focuses on the computer system architecture of buses. The research is based on the buses which used by AMD K computer system. Those are includes bus characteristics, bus arbitration and bus topology. 本报告重点介绍公交车的计算机系统架构。 该研究基于AMD K计算机系统所使用的公共汽车的。 这些包括公共汽车的特性、公共汽车的仲裁和公共汽车的拓扑。 In bus characteristics, we had cover the bus width and bus speed, types of buses and bus lines, and also advantages and disadvantages of a “bus” to a “network”. In bus arbitration, there was include purpose of arbitration, how does the arbitration protocol work and multiplexing. Other else was the bus topology. In the end of the report, there was a summarize results which include why a bus hierarchy is required, how a bus hierarchy works and additional hardware circuitry required. Introduction This assignment is mainly explaining a fundamental architectural feature present in all computer system, buses. Buses have historically provided a flexible communications structure in computer systems. 该作业主要解释存在于所有计算机系统、公共汽车的中的基本架构特征。 公共汽车的历来在计算机系统中提供了灵活的通信结构。 Furthermore, buses in computing are a digital communication mechanism that allows two or more functional units to transfer control signals or data. Most buses are designed for use inside a single computer system; some are used within a single integrated circuit. Many bus designs exist because a bus can be optimized for a specific purpose. For example, a memory bus is intended to interconnect a processor with a memory system and an I/O bus is intended to interconnect a processor with set of I/O devices. Furthermore, buses can be divided into two major groups based on their control. Those two groups are local buses and system buses. Various bus designs have been used in the PC, including ISA, EISA, Micro Channel, VL-bus and PCI. Other peripheral busses are NuBus, TURBOchannel, VMEbus, MULTIBUS and STD bus. Bus Width A bus is characterized by the amount of information that can be transmitted at once. It is call bus width. The amount expressed in bits, corresponds to the number of physical lines over which data is sent simultaneously. The term “width” is used to refer to the number of bits that a bus can transmit at once. Typical widths are 8, 16, 32, or 64 bits at a time. 公共汽车的的特点是可以一次传输的信息量。 它是呼叫公共汽车的宽度。 以比特表示的数量对应于同时发送数据的物理线路的数量。 术语“宽度”用于指公共汽车的一次可以传输的位数。 典型宽度为一次 8、16、32 或 64 位。 In other words, the bus width means the size of the entity that the bus sends data in one cycle. For example 32 bits, this means that the bus has 32 wires that are used for the transmission. (This may also be different, depending on the transmission protocol). Bus Speed Bus speed means how many bits or bytes (1 byte = 8 bits) is the bus able to send in a unit of time (typically second). For example for a computer network it could be 100 Mbs means 100 Megabits (12, 5 Megabytes) in a second. The bus speed is also defined by its frequency. It expressed in Hertz. Frequency means the number of data packets sent or received per second. Each time that data is sent or received is called a cycle. 公共汽车的速度是指公共汽车的在单位时间（通常是秒）内能够发送多少位或字节（1 字节 = 8 位）。 例如，对于计算机网络，它可能是 100 Mbs 意味着每秒 100 兆位（12、5 兆字节）。 公共汽车的速度也由其频率定义。 它以赫兹表示。 频率是指每秒发送或接收的数据包的数量。 每次发送或接收数据称为一个周期。 Besides, the bus speeds also commonly known as front side bus (FSB). It is shows how fast the components can communicate with each other. Faster bus speed means faster computer. You can easily see how a faster FSB helps your computer get more information from one place to the other. For example, if two computers are exactly the same in all ways except one has an FSB speed of 500 MHz and the other has an FSB of 1066 MHz, twice as much data will get through on the second computer compared to the first. This means your computer will get more work done in the same amount of time faster spreadsheet calculations, faster decoding of that movie, or smoother video games. To increase the bus speed you can either increase the bus width or the frequency of the transmission on the bus. The Different Types of Buses Local Buses A local bus is the simplest buses consist of set of wires. Within the central processing unit (CPU), local buses can generally be divided in three types. They are address buses, data buses or control buses. 当地巴士 本地公共汽车的是由一组电线组成的最简单的公共汽车的。 在中央处理器（CPU）内部，本地公共汽车的一般可以分为三种类型。 它们是地址公共汽车的、数据公共汽车的或控制公共汽车的。 Address buses tend to be specialized in purpose and are usually unidirectional. It carries an address from the CPU to memory or I/O devices. Data buses tend to be more general in purpose and are bidirectional. It carries data between the CPU and memory or I/O devices. Control buses carry signals from the control unit to other components of the computer and back to control unit. System Buses Unlike local buses, system buses are independent functional components of many computers. Each system bus has its own control circuit, called a bus controller, and within each bus controller is an arbiter, which process requests to use the bus. The bus controller may be distributed among the devices that use the bus. Systems buses generally connect system components together, such as the CPU,I/O system and often the main-memory system, and designers often optimize system buses for transferring data between I/O devices and main-memory. 与本地公共汽车的不同，系统公共汽车的是许多计算机的独立功能组件。 每个系统公共汽车的都有自己的控制电路，称为公共汽车的控制器，每个公共汽车的控制器内部都有一个仲裁器，它处理使用公共汽车的的请求。 公共汽车的控制器可以分布在使用公共汽车的的设备之间。 系统公共汽车的通常将系统组件连接在一起，例如 CPU、I/O 系统和主存系统，设计人员经常优化系统公共汽车的以在 I/O 设备和主存之间传输数据。 A key distinction between system buses and local buses is that system buses tend to have well-documented and stable definitions, so that designers can attach a wide variety of devices to them. Local buses are processor-specific and not widely documented. They tend to be proprietary. Example of system buses are DEC UNIBUS and the Apple NuBus. Bus Lines The wires that comprise a bus are called lines. Four main categories of bus lines : Data lines – Carry data from one place to another. Address lines – Specify the recipient of data on the bus. Control lines – Provide control for the synchronization and operation of the bus and the modules to which it is connected. Power lines – Provide power to various components connected to the bus. Advantages / Disadvantages of a “Bus” to a “Network” Data bus networks have quite a few advantages compare the other network topologies such as point-to-point links in these applications. Generally, a data bus can make possible the interconnection of a set of terminals when the number of terminals is so large that interconnection through individual point-to-point links becomes unusable. Furthermore, a data bus topology can provide large configurationally flexibility. Terminals can be added to the network or moved to different locations without major revisions in the cabling layout. Both of these advantages are of particular importance in applications in which cable installation is the dominant system cost, for example in shipboard applications. Purpose of arbitration In a computer system, all the devices communicate with the other device are connected to the main board over a same bus. If two or more I/O (input and output) devices try to use the bus at the same time to access the main board, there will be a conflict arise. Therefore, bus arbitration is created is to resolve the problem. Bus arbiter is a circuit to coordinate the activities of devices request for memory transfer using the bus. The process that runs by bus arbiter is name as Bus Arbitration. It is to prevent two or more I/O devices initiating transfers at the same time. The bus arbitration mechanism is designed to allow high priority devices such as the processor and RAM get first access to the bus, while the other devices (disks, video cards, sound cards etc.) get lower priority, and often have to wait to access the bus. The prioritization is according numbered interrupts to priority systems. The lower the numbered interrupts will has the higher priority. On many systems, the CPU has interrupt 0. Therefore, CPU always goes first on the bus. Meanwhile, there are time slices provided over the bus. How does the arbitration protocol work The device that uses to allow for initiating data transfers on the bus is called as bus master. Therefore, only one bus master can exist at a time. When the bus master relinquished its control, the other device also can act as bus master. However, the process of transferring the bus mastership from one device to another device has to coordinate carefully to take account of the needs of various devices. As stated earlier, the bus arbitration has been design to use by high priority device. Therefore, scheduling function will be performs by bus arbiter. Bus arbiter can be part of the processer or separate unit that connected to bus. 用于允许在公共汽车的上启动数据传输的设备称为公共汽车的主机。 因此，一次只能存在一个公共汽车的主控器。 当公共汽车的主控器放弃其控制权时，其他设备也可以充当公共汽车的主控器。 然而，将公共汽车的控制权从一个设备转移到另一个设备的过程必须仔细协调以考虑各种设备的需求。 如前所述，公共汽车的仲裁被设计为供高优先级设备使用。 因此，调度功能将由公共汽车的仲裁器执行。 公共汽车的仲裁器可以是处理器的一部分，也可以是连接到公共汽车的的独立单元。 The diagram above show a basic arrangement example of processor contains the bus arbiter circuitry. In this case, the processor is act as the bus master. However in some cases, the other DMA (direct memory access) controller can gain the bus mastership. DMA controllers activate the Bus-request line, BR before it gain the bus mastership. The Signal of Bus- request line is transfer using the logical OR concept from the bus-request line to the other I/O devices. When the bus request is activated, the processor will activates the bus Grant signal, BG1, gives permission to the DMA controller use the bus when it become free. The signal is using a daisy-chain arrangement to connect all DMA controllers. Therefore, when DMA controller 1 request for the bus, it will block the propagation of the grant signal to other I/O device automatically. Else, it will assert BG2 to grant downstream. The bus master indicates all I/O devices that it is using the bus by activating another open collector line call as Bus Busy, BBSY. Therefore, a DMA controller need to wait for Bus busy to inactive after the Bus Grant signal send. In the situation, the DMA controller can assumes the bus mastership. Multiplexing Multiplexed bus is a type of bus structure which the number of signal lines represented by the bus is less than the number of bits of data, addresses, and control information being transferred between devices of the computer system. For example, if a multiplexed address bus use 8 signal lines to transmit 16 bits of address information. The information is transferred sequentially where the additional control line is being used for sequencing the transfer. 多路复用公共汽车的是一种公共汽车的结构，它所代表的信号线的数量少于计算机系统设备之间传输的数据、地址和控制信息的位数。 例如，如果多路复用地址公共汽车的使用 8 条信号线来传输 16 位地址信息。 在使用附加控制线对传输进行排序的情况下，按顺序传输信息。 In another example, the system represent a master control unit (MCU) connecting to one or more receiver-transmit unit (RTU) by a data bus. The MCU transmits a message to the RTU for comprising a synchronization pulse of known duration and successive time spaced timing signals separated by time duration T marking the boundaries of data bits to be transmitted from the RTU to the MCU. The RTU is including a clock pulse source which utilizes the synchronization pulse to determine the frequency of the clock pulse source in P pulses per duration T. The value P is used in conjunction with the timing signals to create properly timed data determining signals in the data bits. Point to point topology Point to point (PTP) is directly connects two nodes to together. Following is some example of using PTP to connect 2 nodes together. 点对点（PTP）是直接将两个节点连接在一起。 以下是使用 PTP 将 2 个节点连接在一起的一些示例。 Two computers communicating via modems. A mainframe terminal communicating with a front end processor. A workstation communicating along a parallel cable to a scanner. In a point-to-point topology, all the devices are connected with a shared switch. The switch is different from the shared topology. Computational components that are connected using a point-to-point topology do not need to use any type of bus arbitration scheme. Instate, the shared switch breaks the continuous stream of data on the bus into data packets that are routed to the individual devices. Using this method, the shared switch able establishes point-to-point connections between the different devices. From an individual device’s perspective, a connection has to be a private, direct, continuous connection to another device. The connection may comprise one or more two-way of serial-connections. By increasing the number of lanes of a connection, therefore the bandwidth of the connection can by increase. An example of point-to-point bus topology is the implementation in peripheral component interface expresses (“PCI Express”). PCI Express is a computer expansion card standard designed to replace the older PCI, PCI-X, and AGP standards. It was introduced by Intel in 2004, PCIe is the latest standard for expansion cards that is available on mainstream personal computers. Multipoint Multipoint is a bus topologies that carries signals to several destinations. It is also known as multidrop bus (MDB) or broadcast bus. Multipoint bus usually requires addressing signals on the bus to identify the addressed destination. Example : Ethernet. It is also a computer bus in which all components are connected to same set of electrical wires. 多点是一种将信号传送到多个目的地的公共汽车的拓扑。 它也称为多点公共汽车的 (MDB) 或广播公共汽车的。 多点公共汽车的通常需要公共汽车的上的寻址信号来识别寻址的目的地。 示例：以太网。 它也是一种计算机公共汽车的，其中所有组件都连接到同一组电线。 Summary From this assignment, we had classified out the type of buses which it’s basically grouped into four parts known as processor bus, cache bus, local I/O bus and standard I/O bus. Each of this is different as processor bus is the highest-level bus that the chipset uses to send information to and from the processor. 从这个任务中，我们将公共汽车的的类型分类出来，它基本上分为四个部分，分别是处理器公共汽车的、缓存公共汽车的、本地 I/O 公共汽车的和标准 I/O 公共汽车的。 每个都不同，因为处理器公共汽车的是芯片组用来向处理器发送信息和从处理器发送信息的最高级别公共汽车的。 While, cache bus used to accessing the system cache. At the same time, the local I/O bus is for connecting performance-critical peripherals to the memory, chipset, and processor such as video cards and disk storage devices. Example of local I/O bus is like Peripheral Component Interconnect Bus (PCI). Last would be the standard I/O bus which it used for slower peripherals such as modems while it also for compatibility with older devices. Bus hierarchy is required due to the lower level bus like local and standard I/O buses need to steps by steps sent the data to the upper levels of buses in order to allow users to retrieve or transfer the data from each particular memory to another. Hence, I consider them a hierarchy because each bus is to some extent further removed from the processor; each one connects to the level above it, integrating the various parts of the PC together. Each one is also generally slower than the one above it. As a conclusion, bus is generally designed for multiple devices to share the medium. Furthermore, additional hardware circuitry is needed because of that may have problems when two clients want to transmit at the same time on the same bus. Therefore, hardware like bus arbitration is needed to overcome this conflict. Conclusion As a conclusion, buses are actually helpful as its act as a vital medium in order to transferring data. Basically, buses connect different modules within the CPU and to memory and other I/O peripherals. Meanwhile, buses can also connect two different components at the same time through the usage of point-to-point or multipoint. 总而言之，公共汽车的实际上是有用的，因为它是传输数据的重要媒介。 基本上，公共汽车的将 CPU 内的不同模块连接到内存和其他 I/O 外围设备。 同时，公共汽车的还可以通过点对点或多点的使用同时连接两个不同的组件。 Buses can carry data, address and control function as it could transmit the instructions of the users into the outputs. Buses are form in the combination of data line, address line, power line and control line. Then, buses and buses communicate through a medium called bridge. Further, we had identified the characteristics of the buses as it categorized into two categories. For bus speed, it covers the area for speed of transmitting data to another medium. While, bus width is the amount of data can be transferring. Besides, type of buses, pros and cons of bus and network and buses arbitration also included within our report. Lastly, we had also stated out the purposes of buses arbitration. Frequently Ask Question (FAQ) What is a bus? How to solve the conflict of different data is being transferring through the same bus but at different devices? What are the functions of buses? How to measure the speed of transferring or retrieving data from buses? How does buses connected to each other? How to increase the buses speed? Which method allows buses to connect 2 devices? 什么是巴士？ 如何解决不同数据在同一公共汽车的不同设备传输的冲突？ 公交车的作用是什么？ 如何测量从公共汽车的传输或检索数据的速度？ 公共汽车如何相互连接？ 如何提高公交车速度？ 哪种方法允许公共汽车的连接 2 个设备？ 留学生Essay相关专业范文素材资料,尽在本网，可以随时查阅参考。本站也提供多国留学生课程作业写作指导服务,如有需要可咨询本平台。 |
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