[中英对照]How PCI Works | PCI工作原理

How PCI Works | PCI工作原理

Your computer's components work together through a bus. 
Learn about the PCI bus and PCI card, such as the one above. 
See more computer hardware pictures.

The power and speed of computer components has increased at a steady rate since desktop computers were first developed decades ago. Software makers create new applications capable of utilizing the latest advances in processor speed and hard drive capacity, while hardware makers rush to improve components and design new technologies to keep up with the demands of high-end software.

自台式计算机数十年前开始发展以来，计算机部件的功率和速度一直在稳步增长。软件制造商开发了新的应用程序以充分利用处理器的速度和硬盘容量，而硬件制造商则急于改进计算机部件和设计新的技术，以满足高端软件的需求。

There's one element, however, that often escapes notice - the bus. Essentially, a bus is a channel or path between the components in a computer. Having a high-speed bus is as important as having a good transmission in a car. If you have a 700-horsepower engine combined with a cheap transmission, you can't get all that power to the road. There are many different types of buses.

然而，有一个因素经常被忽略 -- 那就是总线(Bus)。总线本质上是计算机中各组件之间的通道或通路。对计算机来说，拥有高速Bus，和在汽车里有一个好的变速器同样重要。如果你有一个700马力的发动机，但是却有一个便宜的变速器，你就不能开足所有马力在道路上驰骋。总线(Bus)种类有许多。

The idea of a bus is simple -- it lets you connect components to the computer's processor. Some of the components that you might want to connect include hard disks, memory, sound systems, video systems and so on. For example, to see what your computer is doing, you normally use a CRT or LCD screen. You need special hardware to drive the screen, so the screen is driven by a graphics card. A graphics card is a small printed circuit board designed to plug into the bus. The graphics card talks to the processor using the computer's bus as a communication path.

总线的概念其实很简单 -- 有了总线, 你就可以把计算机部件连接到处理器上。你可能需要连接这样一些组件，例如硬盘、内存、声音系统、视频系统等。举个例子，要查看计算机正在做什么，通常使用CRT或LCD显示屏。驱动显示屏需要特殊的硬件，所以显示屏是由显卡驱动的。图形卡是为插入到总线上而设计的小型印刷电路板，它把计算机总线作为通信线路与处理器交谈。

The advantage of a bus is that it makes parts more interchangeable. If you want to get a better graphics card, you simply unplug the old card from the bus and plug in a new one. If you want two monitors on your computer, you plug two graphics cards into the bus. And so on.

总线的优点是使零部件可更换。如果你想得到更好的图形卡，你只需要把旧图形卡从总线上拔出来，然后插入一个新的图形卡。如果你想在计算机上安装两个显视器，你可以在总线上插入两个图形卡。凡此种种，不一而足。

In this article, you will learn about some of those buses. We will concentrate on the bus known as the Peripheral Component Interconnect (PCI). We'll talk about what PCI is, how it operates and how it is used, and we'll look into the future of bus technology.

在本文中，您将了解到一些总线。我们将集中于PCI(外围设备组件互连)总线。我们将讨论PCI是什么，它是如何运行的，以及它是如何被使用的。我们还将探讨一下总线技术的未来。

1. System Bus vs. PCI Bus | 系统Bus vs. PCI Bus

The illustration above shows how the various buses connect to the CPU.

Twenty or 30 years ago, the processors were so slow that the processor and the bus were synchronized -- the bus ran at the same speed as the processor, and there was one bus in the machine. Today, the processors run so fast that most computers have two or more buses. Each bus specializes in a certain type of traffic.

二三十年前，处理器很慢，因此处理器和总线是同步的。总线运行速度和处理器运行速度相同，且机器中只有一根总线。时至今天，处理器运行得如此之快以至于大多数计算机都有两个以上总线。每一个总线都专门负责某一种交通运输。

A typical desktop PC today has two main buses:

The first one, known as the system bus or local bus, connects the microprocessor (central processing unit) and the system memory. This is the fastest bus in the system.
The second one is a slower bus for communicating with things like hard disks and sound cards. One very common bus of this type is known as the PCI bus. These slower buses connect to the system bus through a bridge, which is a part of the computer's chipset and acts as a traffic cop, integrating the data from the other buses to the system bus.

典型的台式机有两条主要的总线：

第一条，称为系统总线(或本地总线, 注：有的文献中将system bus与local bus区分开来，用local bus指代慢速总线)，连接微处理器(中央处理器)和系统内存。这是系统中最快的总线。
第二条，较慢的总线，用于与硬盘和声卡等通信。在这种类型的总线中，一种非常常见的总线称之为PCI总线。这些较慢的总线通过桥接器连接到系统总线，该桥是计算机芯片组的一部分，充当交通警察，将其他总线的数据与系统总线集成起来。

Technically there are other buses as well. For example, the Universal Serial Bus (USB) is a way of connecting things like cameras, scanners and printers to your computer. It uses a thin wire to connect to the devices, and many devices can share that wire simultaneously. Firewire is another bus, used today mostly for video cameras and external hard drives.

从技术上讲，还有其他总线。例如，USB(通用串行总线)是一种将照相机、扫描仪和打印机等连接到计算机上的方法。它使用细导线连接设备，许多设备可以同时共享该导线。火线是另一种总线，主要用于摄像机和外部磁盘驱动器。

Next, learn about the history of PCI buses.

接下来，我们将聊聊PCI总线的历史。

2. PCI History | PCI的历史

The original PC bus in the original IBM PC (circa 1982) was 16 bits wide and operated at 4.77 MHz. It officially became known as the ISA bus. This bus design is capable of passing along data at a rate of up to 9 MBps (megabytes per second) or so, fast enough even for many of today's applications.

最初的PC总线源于IBM PC(大约在1982年)，16位宽，工作频率为4.77 MHz。这一总线后来正式成为ISA总线。这一总线设计能够以每秒9MB的速率传输数据，对今天的许多应用程序来说,甚至也是足够快的。

Several years ago, the ISA bus was still used on many computers. That bus accepted computer cards developed for the original IBM PC in the early 1980s. The ISA bus remained in use even after more advanced technologies were available to replace it.

在几年前，ISA总线仍使用在许多计算机上。这一总线是在80年代初为原始的IBM PC开发的。即使后来采用更先进的技术来替代它，ISA总线仍在使用之中。

There were a couple of key reasons for its longevity:

Long-term compatibility with a large number of hardware manufacturers.
Before the rise of multimedia, few hardware peripherals fully utilized the speed of the newer bus.

ISA总线之所以能够如此长寿，是因为有如下几个关键原因：

大量硬件制造商对它保持了长期的兼容性。
在多媒体兴起之前，很少有硬件外部设备能够充分利用较新的总线速度。

As technology advanced and the ISA bus failed to keep up, other buses were developed. Key among these were Extended Industry Standard Architecture (EISA) -- which was 32 bits at 8 MHz-- and Vesa Local Bus (VL-Bus). The cool thing about VL-Bus (named after VESA, the Video Electronics Standards Association, which created the standard) is that it was 32 bits wide and operated at the speed of the local bus, which was normally the speed of the processor itself. The VL-Bus essentially tied directly into the CPU. This worked okay for a single device, or maybe even two. But connecting more than two devices to the VL-Bus introduced the possibility of interference with the performance of the CPU. Because of this, the VL-Bus was typically used only for connecting a graphics card, a component that really benefits from high-speed access to the CPU.

伴随着技术的进步，ISA总线就落伍了，于是其他总线被开发出来。其中的关键总线是EISA(扩展工业标准体系结构)总线(32位宽，8 MHz)和VL总线(VESA局部总线)。VL总线(VESA,视频电子标准协会制定的标准)最酷的是32位宽，本地总线速度通常是处理器本身的速度。VL总线本质上是直接连接到CPU上。这对一个设备，或者甚至两个都是有效的。但是，将两个以上的设备连接到VL总线可能会干扰CPU的性能。正因为如此，VL总线通常只用于连接图形卡。图形卡是一个真正得益于高速访问CPU的组件。

During the early 1990s, Intel introduced a new bus standard for consideration, the Peripheral Component Interconnect (PCI) bus. PCI presents a hybrid of sorts between ISA and VL-Bus. It provides direct access to system memory for connected devices, but uses a bridge to connect to the frontside bus and therefore to the CPU. Basically, this means that it is capable of even higher performance than VL-Bus while eliminating the potential for interference with the CPU.

在20世纪90年代初，Intel引入了一种新的总线标准，即PCI(外围组件互连)总线。PCI融合了ISA和VL总线，用桥连接到前端总线进而连接到CPU，为外围设备提供了直接访问系统内存的能力。这基本上意味着PCI总线能够比VL总线有更高的性能，同时消除了与CPU相干扰的可能性。

Learn more about the development of the PCI bus and PCI card on the next page.

在下一页中，我们将介绍有关PCI总线和PCI卡的开发。

3. Frontside Bus, Backside Bus and PCI Cards

Bus Types

The frontside bus is a physical connection that actually connects the processor to most of the other components in the computer, including main memory (RAM), hard drives and the PCI slots. These days, the frontside bus usually operates at 400-MHz, with newer systems running at 800-MHz.

前端总线实际上是一个物理连接，连接处理器和计算机的其他部件，包括内存、硬盘和PCI插槽。现如今，前端总线通常工作在400-MHz，更新的系统运行在800-MHz。

The backside bus is a separate connection between the processor and the Level 2 cache. This bus operates at a faster speed than the frontside bus, usually at the same speed as the processor, so all that caching works as efficiently as possible. Backside buses have evolved over the years. In the 1990s, the backside bus was a wire that connected the main processor to an off-chip cache. This cache was actually a separate chip that required expensive memory. Since then, the Level 2 cache has been integrated into the main processor, making processors smaller and cheaper. Since the cache is now on the processor itself, in some ways the backside bus isn't really a bus anymore.

后端总线是处理器与二级高速缓存之间的独立连接。后端总线比前端总线速度更快，通常速度与处理器相同，因此所有的缓存都尽可能地有效地工作。这些年来，后端总线逐渐发展起来了。在20世纪90年代，后端总线是连接处理器和芯片外缓存的一根导线。这个缓存实际上是一个需要昂贵内存支撑的独立芯片。从那时起，二级缓存被集成到处理器中，使得处理器更小更便宜。由于缓存现在在处理器本身，在某种程度上看来，后端总线已经不再是真正的总线了。

PCI can connect more devices than VL-Bus, up to five external components. Each of the five connectors for an external component can be replaced with two fixed devices on the motherboard. Also, you can have more than one PCI bus on the same computer, although this is rarely done. The PCI bridge chip regulates the speed of the PCI bus independently of the CPU's speed. This provides a higher degree of reliability and ensures that PCI-hardware manufacturers know exactly what to design for.

PCI可以比VL总线连接更多的设备，多达五个外部组件。五个外部组件的每一个都可以用主板上的两个固定设备替换。此外，你还可以在同一台计算机上使用多个PCI总线，虽然很少有人这么做。PCI桥芯片负责调节PCI总线的速度，独立于CPU速度。这提供了更高的可靠性，并确保PCI硬件制造商能够确切地知道要设计什么。

PCI originally operated at 33 MHz using a 32-bit-wide path. Revisions to the standard include increasing the speed from 33 MHz to 66 MHz and doubling the bit count to 64. Currently, PCI-X provides for 64-bit transfers at a speed of 133 MHz for an amazing 1-GBps (gigabyte per second) transfer rate!

PCI最初使用32位宽，工作在33MHz。该标准的修订包括将速度从33MHz提升到66MHz，并将位宽扩展到64位。目前，PCI-X提供64位宽，工作在133MHz，传输速率那是相当惊人，可达1-Gbps(1G字节/每秒)。

PCI cards use 47 pins to connect (49 pins for a mastering card, which can control the PCI bus without CPU intervention). The PCI bus is able to work with so few pins because of hardware multiplexing, which means that the device sends more than one signal over a single pin. Also, PCI supports devices that use either 5 volts or 3.3 volts.

PCI卡使用47个引脚连接(控制卡49个引脚，可以控制PCI总线而无需CPU的干预)。由于硬件多路复用，PCI总线能够借助很少的引脚就工作，这意味着该设备在一个引脚上能发送多个信号。此外，PCI支持电压为5伏或3.3伏的设备。

PCI cards use 47 pins.

Although Intel proposed the PCI standard in 1991, it did not achieve popularity until the arrival of Windows 95 (in 1995). This sudden interest in PCI was due to the fact that Windows 95 supported a feature called Plug and Play (PnP), which we'll talk about in the next section.

虽然英特尔在1991年就提出了PCI标准，但它直到1995年(Win95到来)才流行起来。对PCI突然感兴趣，是因为Win95支持一种称为即插即用(PnP)的特性，我们将在下一节予以讨论。

4. Plug and Play | 即插即用

Plug and Play (PnP) means that you can connect a device or insert a card into your computer and it is automatically recognized and configured to work in your system. PnP is a simple concept, but it took a concerted effort on the part of the computer industry to make it happen. Intel created the PnP standard and incorporated it into the design for PCI. But it wasn't until several years later that a mainstream operating system, Windows 95, provided system-level support for PnP. The introduction of PnP accelerated the demand for computers with PCI, very quickly supplanting ISA as the bus of choice.

即插即用(PnP)意味着你可以将一个设备连接到或将一张卡插入到你的计算机，该设备或者卡会被自动识别并配置到系统中去，然后就可以正常工作了。PnP的概念很简单，但践行这一概念需要计算机行业的共同努力。英特尔创建了PnP标准并将其纳入到PCI的设计中。但相隔几年后才有一个主流操作系统(Windows 95)为PnP提供了系统级的支持。PnP的引入加速了计算机对PCI总线的需求，于是PCI总线很快取代了ISA总线。

To be fully implemented, PnP requires three things:

完全实现PnＰ, 需要如下三个方面的支持：

PnP BIOS - The core utility that enables PnP and detects PnP devices. The BIOS also reads the ESCD for configuration information on existing PnP devices.

即插即用BIOS - 支持即插即用(PnP)和检测PnP设备的核心工具。BIOS同时也读取ESCD从而获取PnP设备上的配置信息。

Extended System Configuration Data (ESCD) - A file that contains information about installed PnP devices.

扩展系统配置数据(ESCD) - 包含了已经安装的PnP设备的信息的文件。

PnP operating system - Any operating system, such as Windows XP, that supports PnP. PnP handlers in the operating system complete the configuration process started by the BIOS for each PnP device. PnP automates several key tasks that were typically done either manually or with an installation utility provided by the hardware manufacturer. These tasks include the setting of:

Interrupt requests (IRQ) - An IRQ, also known as a hardware interrupt, is used by the various parts of a computer to get the attention of the CPU. For example, the mouse sends an IRQ every time it is moved to let the CPU know that it's doing something. Before PCI, every hardware component needed a separate IRQ setting. But PCI manages hardware interrupts at the bus bridge, allowing it to use a single system IRQ for multiple PCI devices.
Direct memory access (DMA) - This simply means that the device is configured to access system memory without consulting the CPU first.
Memory addresses - Many devices are assigned a section of system memory for exclusive use by that device. This ensures that the hardware will have the needed resources to operate properly.
Input/Output (I/O) configuration - This setting defines the ports used by the device for receiving and sending information.

操作系统支持PnP - 任何支持PnP的操作系统，例如WindowsXP。操作系统中的PnP handler负责配置BIOS启动时枚举到的每一个PnP设备。PnP将几个关键任务自动化，这些关键任务通常是由手动完成或者由硬件制造商提供的安装工具完成。这些任务包括：

中断请求(IRQ) - IRQ，也称为硬件中断，被计算机的各个部件用来引起CPU的注意。例如，鼠标每一次移动，都会发送一个IRQ，让CPU知道它在做什么。在PCI之前，每一个硬件组件都需要设置一个单独的IRQ。有了PCI之后，PCI在总线桥上管理硬件中断，这就允许它对多个PCI设备使用一个系统IRQ。
直接内存访问(DMA) - 这意味着配置设备去访问系统内存的话，不需要事先咨询CPU。
内存地址 - 很多设备都要求分配一部分系统内存做排他性的使用。这确保了硬件拥有它所必需的资源从而得以正常运作。
I/O配置 - 这一设置定义了设备用于接收和发送信息所使用的端口。

While PnP makes it much easier to add devices to your computer, it is not infallible.
有了PnP，添加一个计算机设备变得更容易，但并非万无一失。

Variations in the software routines used by PnP BIOS developers, PCI device manufacturers and Microsoft have led many to refer to PnP as "Plug and Pray." But the overall effect of PnP has been to greatly simplify the process of upgrading your computer to add new devices or replace existing ones.

PnP BIOS开发人员使用的软件例程是不断变化的，因此PCI设备制造商和微软让很多人在提到PnP(Plug and Play)的时候，PnP成为了"Plug and Pray"。但是，PnP的总体效果还是不错的，它大大简化了在升级计算机的时候添加一个新设备或者替换一个现有的设备的过程。

PCI vs. AGP

The PCI bus was adequate for many years, providing enough bandwidth for all the
peripherals most users might want to connect. All except one: graphics cards.
In the mid 1990s, graphics cards were getting more and more powerful, and 3D
games were demanding higher performance. The PCI bus just couldn't handle all
the information passing between the main processor and the graphics processor.
As a result, Intel developed the Accelerated Graphics Port (AGP). AGP is a bus
dedicated completely to graphics cards. The bandwidth across the AGP bus isn't
shared with any other components. Although PCI continues to be the bus of choice
for most peripherals, AGP has taken over the specialized task of graphics
processing. However, a new bus technology has hit the market that just might
spell the end for AGP. More on this later in the article, stay tuned...

5. Adding a PCI Device | 添加一个PCI设备

This motherboard has four PCI slots.

Let's say that you have just added a new PCI-based sound card to your Windows XP computer. Here's an example of how it would work.

You open up your computer's case and plug the sound card into an empty PCI slot on the motherboard.
You close the computer's case and power up the computer.
The system BIOS initiates the PnP BIOS.
The PnP BIOS scans the PCI bus for hardware. It does this by sending out a signal to any device connected to the bus, asking the device who it is.
The sound card responds by identifying itself. The device ID is sent back across the bus to the BIOS.
The PnP BIOS checks the ESCD to see if the configuration data for the sound card is already present. Since the sound card was just installed, there is no existing ESCD record for it.
The PnP BIOS assigns IRQ, DMA, memory address and I/O settings to the sound card and saves the data in the ESCD.
Windows XP boots up. It checks the ESCD and the PCI bus. The operating system detects that the sound card is a new device and displays a small window telling you that Windows has found new hardware and is determining what it is.
In many cases, Windows XP will identify the device, find and load the necessary drivers, and you'll be ready to go. If not, the "Found New Hardware Wizard" will open up. This will direct you to install drivers off of the disc that came with the sound card.
Once the driver is installed, the device should be ready for use. Some devices may require that you restart the computer before you can use them. In our example, the sound card is immediately ready for use.
You want to capture some audio from an external tape deck that you have plugged into the sound card. You set up the recording software that came with the sound card and begin to record.
The audio comes into the sound card via an external audio connector. The sound card converts the analog signal to a digital signal.
The digital audio data from the sound card is carried across the PCI bus to the bus controller. The controller determines which device on the PCI device has priority to send data to the CPU. It also checks to see if data is going directly to the CPU or to system memory.
Since the sound card is in record mode, the bus controller assigns a high priority to the data coming from it and sends the sound card's data over the bus bridge to the system bus.
The system bus saves the data in system memory. Once the recording is complete, you can decide whether the data from the sound card is saved to a hard drive or retained in memory for additional processing.

假定您添加了一个新的基于PCI的声卡到您的Windows XP计算机。下面举例说明它是如何工作的。

打开计算机的机箱，将声卡插入主板上一个空的PCI插槽中。
关上机箱，给计算机上电。
系统BIOS初始化PnP BIOS。
PnP BIOS扫描硬件PCI总线。它给连接到总线上的每一个设备发送信号，询问设备是谁。
声卡对PnP BIOS的询问做出应答，把设备ID通过总线发送给PnP BIOS。
PnP BIOS检查ESCD, 看看声卡配置数据是否已经存在。因为声卡是刚刚安装的，所以ESCD中没有它的记录。
PnP BIOS给声卡分配IRQ、DMA、内存地址和I/O设置，并保存到ESCD中。
WindowsXP启动，检查ESCD和PCI总线。操作系统检测到声卡是一个新的设备，并弹出一个小窗口告诉用户找到了一个新的硬件并正在确认它是什么硬件。
在多数情况下，Windows XP将识别设备，找到并加载对应的驱动程序，然后用户就可以开始使用这个设备了。否则的话，"找到新的硬件向导"将被弹出，提示用户安装声卡驱动程序。
一旦设备驱动程序被安装，设备就可以立即使用。有些设备可能需要重启计算机。在我们的例子中，用户无需重启计算机，可以立即使用声卡。
一旦插好了声卡，您就希望从它的外部磁带面板上捕获一些音频。于是，您设置了录音带的录音软件，然后开始录音。
音频通过外部音频连接器进入声卡。声卡将模拟信号转化为数字信号。
来自声卡的数字音频数据通过PCI总线传输到总线控制器。控制器确定PCI设备上的哪一个设备具有向CPU发送数据的优先权。与此同时，它还检查数据是否直接被送入入CPU还是内存。
由于声卡处于录音模式，总线控制器给来自声卡的数据分配一个高优先级，然后通过总线桥将来自声卡的数据发送给系统总线。
系统总线将来自声卡的数据直接写入到系统内存。一旦录音完毕，您可以选择把这些来自声卡的数据是保存到硬盘上还是保存到内存中以便做进一步的处理。

6. PCI Standards and PCI Express | PCI标准和PCIe

As processor speeds steadily climb in the GHz range, many companies are working feverishly to develop a next-generation bus standard. Many feel that PCI, like ISA before it, is fast approaching the upper limit of what it can do.

随着处理器速度在GHz范围内的稳步攀升，许多公司正在积极开发下一代总线标准。许多人认为PCI就像ISA一样，正在迅速接近它能到达的极限。

All of the proposed new standards have something in common. They propose doing away with the shared-bus technology used in PCI and moving to a point-to-point switching connection. This means that a direct connection between two devices (nodes) on the bus is established while they are communicating with each other. Basically, while these two nodes are talking, no other device can access that path. By providing multiple direct links, such a bus can allow several devices to communicate with no chance of slowing each other down.

提议的所有新标准都存在着共同之处。他们建议废除PCI中使用的共享总线技术，并转向到点到点的交换连接。这意味着总线上的两个设备(结点)之间的直接连接是在它们彼此展开通信时就建立的。基本上可以这么说，当这两个结点在通话时，没有其他的设备可以访问该条会话通路。通过提供多条直接的链路，总线可以允许多个设备同时进行通信而不影响彼此的通信速度。

HyperTransport, a standard proposed by Advanced Micro Devices, Inc. (AMD), is touted by AMD as the natural progression from PCI. For each session between nodes, it provides two point-to-point links. Each link can be anywhere from 2 bits to 32 bits wide, supporting a maximum transfer rate of 6.4 GB per second. HyperTransport is designed specifically for connecting internal computer components to each other, not for connecting external devices such as removable drives. The development of bridge chips will enable PCI devices to access the HyperTransport bus.

HyperTransport是AMD提出的PCI演进标准。对于结点之间的每一个会话，提供两个点到点的链路。每个链路的位宽范围为[2..32], 支持的最大传输速率为6.4GB/s。HyperTransport是专门设计来连接计算机内部组件，不连接外部设备例如移动硬盘。桥芯片的开发，使得PCI设备能够访问HyperTransport总线。

PCI-Express, developed by Intel (and formerly know as 3GIO or 3rd Generation I/O), looks to be the "next big thing" in bus technology. At first, faster buses were developed for high-end servers. These were called PCI-X and PCI-X 2.0, but they weren't suitable for the home computer market, because it was very expensive to build motherboards with PCI-X.

PCIe是由Intel开发的(和以前知道的3GIO或第3代I/O)，看起来仿佛是总线技术领域的"下一件大事"。起初，更快的总线是为高端服务器开发的。这些被称之为PCI-X和PCI-X 2.0，但他们并不适合家用电脑市场，因为构建支持PCI-X的主板很昂贵。

PCI-Express is a completely different beast - it is aimed at the home computer market, and could revolutionize not only the performance of computers, but also the very shape and form of home computer systems. This new bus isn't just faster and capable of handling more bandwidth than PCI. PCI-Express is a point-to-point system, which allows for better performance and might even make the manufacturing of motherboards cheaper. PCI-Express slots will also accept older PCI cards, which will help them become popular more quickly than they would if everyone's PCI components were suddenly useless.

PCIe是一个完全不同的"野兽" -- 它瞄准的是在家用电脑市场，不仅在计算机性能上带来了革命性的突破，而且其外观和构造都非常适合家用计算机系统。这种新的总线不仅速度更快，而且PCI带宽更大。PCIe是一个点对点系统，它允许更好的性能，甚至可能使主板的制造更便宜。PCIe插槽也接受旧的PCI卡，这将有助于PCIe普及变得超乎寻常的迅速，如果每个人的PCI组建突然变得没有用。

It's also scalable. A basic PCI-Express slot will be a 1x connection. This will provide enough bandwidth for high-speed Internet connections and other peripherals. The 1x means that there is one lane to carry data. If a component requires more bandwidth, PCI-Express 2x, 4x, 8x, and 16x slots can be built into motherboards, adding more lanes and allowing the system to carry more data through the connection. In fact, PCI-Express 16x slots are already available in place of the AGP graphics card slot on some motherboards. PCI-Express 16x video cards are at the cutting edge right now, costing more than $500. As prices come down and motherboards built to handle the newer cards become more common, AGP could fade into history.

PCIe还具有可伸缩性。一个基本的PCIe插槽为一个1x连接。这为高速互联连接和其他外围设备提供了足够的带宽。1x意味着有一个通道在传输数据。如果一个组件需要更多的带宽，PCIe 2x，4x，8x和16x插槽可以被内置到主板上，通过增加通道从而使系统能够传输更多的数据。事实上，在某些支持AGP显卡的主板上，PCIe 16x插槽已经有了。现如今，PCIe 16x视频卡处于最前沿，耗资超过500美元。随着价格的下滑和支持新卡的主板越来越普遍，AGP可能会淡出历史舞台。

For more information on PCI and related topics, check out the links on the following page.

有关PIC的更多信息和相关话题，请访问后面一页的链接。

PCI Express and the Future

PCI-Express could mean more than faster computers. As the technology develops,
computer makers could design a motherboard with PCI-Express connectors that
attach to special cables. This could allow for completely modular computer
system, much like home stereo systems. You would have a small box with the
motherboard and processor and a series of PCI-Express connection jacks. An
external hard drive could connect via USB 2.0 or PCI-Express. Small modules
containing sound cards, video cards, and modems could also attach. Instead
of one large box, your computer could be arranged any way you want, and it
would only be as large as the components you need.

7. Lots More Information

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