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.

自臺式計算機數十年前開始發(fā)展以來，計算機部件的功率和速度一直在穩(wěn)步增長。軟件制造商開發(fā)了新的應用程序以充分利用處理器的速度和硬盤容量，而硬件制造商則急于改進計算機部件和設計新的技術，以滿足高端軟件的需求。

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，有一個因素經常被忽略 -- 那就是總線(Bus)。總線本質上是計算機中各組件之間的通道或通路。對計算機來說，擁有高速Bus，和在汽車里有一個好的變速器同樣重要。如果你有一個700馬力的發(fā)動機，但是卻有一個便宜的變速器，你就不能開足所有馬力在道路上馳騁。總線(Bus)種類有許多。

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.

總線的概念其實很簡單 -- 有了總線, 你就可以把計算機部件連接到處理器上。你可能需要連接這樣一些組件，例如硬盤、內存、聲音系統、視頻系統等。舉個例子，要查看計算機正在做什么，通常使用CRT或LCD顯示屏。驅動顯示屏需要特殊的硬件，所以顯示屏是由顯卡驅動的。圖形卡是為插入到總線上而設計的小型印刷電路板，它把計算機總線作為通信線路與處理器交談。

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.

總線的優(yōu)點是使零部件可更換。如果你想得到更好的圖形卡，你只需要把舊圖形卡從總線上拔出來，然后插入一個新的圖形卡。如果你想在計算機上安裝兩個顯視器，你可以在總線上插入兩個圖形卡。凡此種種，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，您將了解到一些總線。我們將集中于PCI(外圍設備組件互連)總線。我們將討論PCI是什么，它是如何運行的，以及它是如何被使用的。我們還將探討一下總線技術的未來。

1. System Bus vs. PCI Bus | 系統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，處理器很慢，因此處理器和總線是同步的?？偩€運行速度和處理器運行速度相同，且機器中只有一根總線。時至今天，處理器運行得如此之快以至于大多數計算機都有兩個以上總線。每一個總線都專門負責某一種交通運輸。

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.

典型的臺式機有兩條主要的總線：

• 第一條，稱為系統總線(或本地總線, 注：有的文獻中將system bus與local bus區(qū)分開來，用local bus指代慢速總線)，連接微處理器(中央處理器)和系統內存。這是系統中最快的總線。
• 第二條，較慢的總線，用于與硬盤和聲卡等通信。在這種類型的總線中，一種非常常見的總線稱之為PCI總線。這些較慢的總線通過橋接器連接到系統總線，該橋是計算機芯片組的一部分，充當交通警察，將其他總線的數據與系統總線集成起來。

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.

從技術上講，還有其他總線。例如，USB(通用串行總線)是一種將照相機、掃描儀和打印機等連接到計算機上的方法。它使用細導線連接設備，許多設備可以同時共享該導線?；鹁€是另一種總線，主要用于攝像機和外部磁盤驅動器。

Next, learn about the history of PCI buses.

接下來，我們將聊聊PCI總線的歷史。

2. PCI History | PCI的歷史

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總線源于IBM PC(大約在1982年)，16位寬，工作頻率為4.77 MHz。這一總線后來正式成為ISA總線。這一總線設計能夠以每秒9MB的速率傳輸數據，對今天的許多應用程序來說,甚至也是足夠快的。

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.

在幾年前，ISA總線仍使用在許多計算機上。這一總線是在80年代初為原始的IBM PC開發(fā)的。即使后來采用更先進的技術來替代它，ISA總線仍在使用之中。

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總線之所以能夠如此長壽，是因為有如下幾個關鍵原因：

• 大量硬件制造商對它保持了長期的兼容性。
• 在多媒體興起之前，很少有硬件外部設備能夠充分利用較新的總線速度。

-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.

伴隨著技術的進步，ISA總線就落伍了，于是其他總線被開發(fā)出來。其中的關鍵總線是EISA(擴展工業(yè)標準體系結構)總線(32位寬，8 MHz)和VL總線(VESA局部總線)。VL總線(VESA,視頻電子標準協會制定的標準)最酷的是32位寬，本地總線速度通常是處理器本身的速度。VL總線本質上是直接連接到CPU上。這對一個設備，或者甚至兩個都是有效的。但是，將兩個以上的設備連接到VL總線可能會干擾CPU的性能。正因為如此，VL總線通常只用于連接圖形卡。圖形卡是一個真正得益于高速訪問CPU的組件。

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世紀90年代初，Intel引入了一種新的總線標準，即PCI(外圍組件互連)總線。PCI融合了ISA和VL總線，用橋連接到前端總線進而連接到CPU，為外圍設備提供了直接訪問系統內存的能力。這基本上意味著PCI總線能夠比VL總線有更高的性能，同時消除了與CPU相干擾的可能性。

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

在下一頁中，我們將介紹有關PCI總線和PCI卡的開發(fā)。

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.

前端總線實際上是一個物理連接，連接處理器和計算機的其他部件，包括內存、硬盤和PCI插槽。現如今，前端總線通常工作在400-MHz，更新的系統運行在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.

后端總線是處理器與二級高速緩存之間的獨立連接。后端總線比前端總線速度更快，通常速度與處理器相同，因此所有的緩存都盡可能地有效地工作。這些年來，后端總線逐漸發(fā)展起來了。在20世紀90年代，后端總線是連接處理器和芯片外緩存的一根導線。這個緩存實際上是一個需要昂貴內存支撐的獨立芯片。從那時起，二級緩存被集成到處理器中，使得處理器更小更便宜。由于緩存現在在處理器本身，在某種程度上看來，后端總線已經不再是真正的總線了。

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總線連接更多的設備，多達五個外部組件。五個外部組件的每一個都可以用主板上的兩個固定設備替換。此外，你還可以在同一臺計算機上使用多個PCI總線，雖然很少有人這么做。PCI橋芯片負責調節(jié)PCI總線的速度，獨立于CPU速度。這提供了更高的可靠性，并確保PCI硬件制造商能夠確切地知道要設計什么。

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位寬，工作在33MHz。該標準的修訂包括將速度從33MHz提升到66MHz，并將位寬擴展到64位。目前，PCI-X提供64位寬，工作在133MHz，傳輸速率那是相當驚人，可達1-Gbps(1G字節(jié)/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個引腳連接(控制卡49個引腳，可以控制PCI總線而無需CPU的干預)。由于硬件多路復用，PCI總線能夠借助很少的引腳就工作，這意味著該設備在一個引腳上能發(fā)送多個信號。此外，PCI支持電壓為5伏或3.3伏的設備。

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.

雖然英特爾在1991年就提出了PCI標準，但它直到1995年(Win95到來)才流行起來。對PCI突然感興趣，是因為Win95支持一種稱為即插即用(PnP)的特性，我們將在下一節(jié)予以討論。

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)意味著你可以將一個設備連接到或將一張卡插入到你的計算機，該設備或者卡會被自動識別并配置到系統中去，然后就可以正常工作了。PnP的概念很簡單，但踐行這一概念需要計算機行業(yè)的共同努力。英特爾創(chuàng)建了PnP標準并將其納入到PCI的設計中。但相隔幾年后才有一個主流操作系統(Windows 95)為PnP提供了系統級的支持。PnP的引入加速了計算機對PCI總線的需求，于是PCI總線很快取代了ISA總線。

To be fully implemented, PnP requires three things:

完全實現PnＰ, 需要如下三個方面的支持：

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)和檢測PnP設備的核心工具。BIOS同時也讀取ESCD從而獲取PnP設備上的配置信息。

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

擴展系統配置數據(ESCD) - 包含了已經安裝的PnP設備的信息的文件。

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.

操作系統支持PnP - 任何支持PnP的操作系統，例如WindowsXP。操作系統中的PnP handler負責配置BIOS啟動時枚舉到的每一個PnP設備。PnP將幾個關鍵任務自動化，這些關鍵任務通常是由手動完成或者由硬件制造商提供的安裝工具完成。這些任務包括：

• 中斷請求(IRQ) - IRQ，也稱為硬件中斷，被計算機的各個部件用來引起CPU的注意。例如，鼠標每一次移動，都會發(fā)送一個IRQ，讓CPU知道它在做什么。在PCI之前，每一個硬件組件都需要設置一個單獨的IRQ。有了PCI之后，PCI在總線橋上管理硬件中斷，這就允許它對多個PCI設備使用一個系統IRQ。
• 直接內存訪問(DMA) - 這意味著配置設備去訪問系統內存的話，不需要事先咨詢CPU。
• 內存地址 - 很多設備都要求分配一部分系統內存做排他性的使用。這確保了硬件擁有它所必需的資源從而得以正常運作。
• I/O配置 - 這一設置定義了設備用于接收和發(fā)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，添加一個計算機設備變得更容易，但并非萬無一失。

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開發(fā)人員使用的軟件例程是不斷變化的，因此PCI設備制造商和微軟讓很多人在提到PnP(Plug and Play)的時候，PnP成為了"Plug and Pray"。但是，PnP的總體效果還是不錯的，它大大簡化了在升級計算機的時候添加一個新設備或者替換一個現有的設備的過程。

PCI vs. AGPThe 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 | 添加一個PCI設備

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.

假定您添加了一個新的基于PCI的聲卡到您的Windows XP計算機。下面舉例說明它是如何工作的。

打開計算機的機箱，將聲卡插入主板上一個空的PCI插槽中。

關上機箱，給計算機上電。

系統BIOS初始化PnP BIOS。

PnP BIOS掃描硬件PCI總線。它給連接到總線上的每一個設備發(fā)送信號，詢問設備是誰。

聲卡對PnP BIOS的詢問做出應答，把設備ID通過總線發(fā)送給PnP BIOS。

PnP BIOS檢查ESCD, 看看聲卡配置數據是否已經存在。因為聲卡是剛剛安裝的，所以ESCD中沒有它的記錄。

PnP BIOS給聲卡分配IRQ、DMA、內存地址和I/O設置，并保存到ESCD中。

WindowsXP啟動，檢查ESCD和PCI總線。操作系統檢測到聲卡是一個新的設備，并彈出一個小窗口告訴用戶找到了一個新的硬件并正在確認它是什么硬件。

在多數情況下，Windows XP將識別設備，找到并加載對應的驅動程序，然后用戶就可以開始使用這個設備了。否則的話，"找到新的硬件向導"將被彈出，提示用戶安裝聲卡驅動程序。

一旦設備驅動程序被安裝，設備就可以立即使用。有些設備可能需要重啟計算機。在我們的例子中，用戶無需重啟計算機，可以立即使用聲卡。

一旦插好了聲卡，您就希望從它的外部磁帶面板上捕獲一些音頻。于是，您設置了錄音帶的錄音軟件，然后開始錄音。

音頻通過外部音頻連接器進入聲卡。聲卡將模擬信號轉化為數字信號。

來自聲卡的數字音頻數據通過PCI總線傳輸到總線控制器。控制器確定PCI設備上的哪一個設備具有向CPU發(fā)送數據的優(yōu)先權。與此同時，它還檢查數據是否直接被送入入CPU還是內存。

由于聲卡處于錄音模式，總線控制器給來自聲卡的數據分配一個高優(yōu)先級，然后通過總線橋將來自聲卡的數據發(fā)送給系統總線。

系統總線將來自聲卡的數據直接寫入到系統內存。一旦錄音完畢，您可以選擇把這些來自聲卡的數據是保存到硬盤上還是保存到內存中以便做進一步的處理。

6. PCI Standards and PCI Express | PCI標準和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.

隨著處理器速度在GHz范圍內的穩(wěn)步攀升，許多公司正在積極開發(fā)下一代總線標準。許多人認為PCI就像ISA一樣，正在迅速接近它能到達的極限。

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.

提議的所有新標準都存在著共同之處。他們建議廢除PCI中使用的共享總線技術，并轉向到點到點的交換連接。這意味著總線上的兩個設備(結點)之間的直接連接是在它們彼此展開通信時就建立的?；旧峡梢赃@么說，當這兩個結點在通話時，沒有其他的設備可以訪問該條會話通路。通過提供多條直接的鏈路，總線可以允許多個設備同時進行通信而不影響彼此的通信速度。

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演進標準。對于結點之間的每一個會話，提供兩個點到點的鏈路。每個鏈路的位寬范圍為[2..32], 支持的最大傳輸速率為6.4GB/s。HyperTransport是專門設計來連接計算機內部組件，不連接外部設備例如移動硬盤。橋芯片的開發(fā)，使得PCI設備能夠訪問HyperTransport總線。

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開發(fā)的(和以前知道的3GIO或第3代I/O)，看起來仿佛是總線技術領域的"下一件大事"。起初，更快的總線是為高端服務器開發(fā)的。這些被稱之為PCI-X和PCI-X 2.0，但他們并不適合家用電腦市場，因為構建支持PCI-X的主板很昂貴。

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是一個完全不同的"野獸" -- 它瞄準的是在家用電腦市場，不僅在計算機性能上帶來了革命性的突破，而且其外觀和構造都非常適合家用計算機系統。這種新的總線不僅速度更快，而且PCI帶寬更大。PCIe是一個點對點系統，它允許更好的性能，甚至可能使主板的制造更便宜。PCIe插槽也接受舊的PCI卡，這將有助于PCIe普及變得超乎尋常的迅速，如果每個人的PCI組建突然變得沒有用。

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還具有可伸縮性。一個基本的PCIe插槽為一個1x連接。這為高速互聯連接和其他外圍設備提供了足夠的帶寬。1x意味著有一個通道在傳輸數據。如果一個組件需要更多的帶寬，PCIe 2x，4x，8x和16x插槽可以被內置到主板上，通過增加通道從而使系統能夠傳輸更多的數據。事實上，在某些支持AGP顯卡的主板上，PCIe 16x插槽已經有了?，F如今，PCIe 16x視頻卡處于最前沿，耗資超過500美元。隨著價格的下滑和支持新卡的主板越來越普遍，AGP可能會淡出歷史舞臺。

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

有關PIC的更多信息和相關話題，請訪問后面一頁的鏈接。

PCI Express and the FuturePCI-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

Related HowStuffWorks Links

• ??? How PCI Express Works
• ??? How AGP Works
• ??? How Motherboards Work
• ??? How IDE Controllers Work
• ??? How USB Works
• ??? How Serial Ports Work
• ??? How Parallel Ports Work
• ??? How Firewire Works

More Great Links

• ??? Technical specifications of PCI-Express
• ??? PC TechGuide: Interfaces
• ??? The PC Guide: PCI
• ??? Infiniband Trade Association
• ??? Rival Plans Stir Rumors of Post-PCI Bus War
• ??? AMD HyperTransport Technology

-Sources

• ??? http://www.xpcgear.com/sapx800xtpciex.html
• ??? http://www.pcstats.com/articleview.cfm?articleID=1087
• ??? http://www.tomshardware.com/graphic/20040310/index.html

Next: How PCI Express Works

轉載于:https://www.cnblogs.com/idorax/p/7472112.html

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