如今， PCI Express是一种流行的技术，许多人都在问它是什么，它的作用是什么，以及为什么支持(PCI Express)PCI Express 4.0的显卡、固态驱动器和主板如此大惊小怪。在本文中，我们将回答这些问题。我们还将尝试阐明什么是PCIe通道、有哪些类型的PCIe插槽以及PCI Express 4.0中的新功能。如果您想了解更多信息，请继续阅读：
什么是PCI Express，它代表什么？
PCI Express代表Peripheral Component Interconnect Express，代表用于将外围硬件连接到计算机主板的标准接口。换言之，PCI Express，或简称PCIe，是将显卡、声卡、以太网和Wi-Fi适配器(graphics cards, sound cards, Ethernet and Wi-Fi adapters)等内部扩展卡(is an interface that connects internal expansion cards)连接到主板的接口。此外(Furthermore)，PCI Express还用于连接某些通常速度非常快的固态驱动器。(solid-state drives)
有哪些类型的PCI Express插槽和尺寸，以及PCIe通道的含义？
为了将扩展卡(expansion card)与主板互连， PCI Express使用物理插槽。我们在主板上看到的常见PCI Express 插槽有(PCI Express slot)PCIe x1、PCIe x4、PCIe x8和PCIe x16。“x”字母后面的数字告诉我们PCI Express 插槽(PCI Express slot)的物理尺寸，而这又取决于其上的针数。数字越大，PCIe 插槽越长，(PCIe slot)扩展卡(expansion card)与插槽互连的针脚就越多。
此外，“x”数字还告诉您该扩展槽中(expansion slot)有多少通道可用。以下是常用PCIe插槽的比较：
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PCIe x1：有1 个通道(1 lane)，18 个引脚，长度为 25 毫米
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PCIe x4：有4 个通道(4 lanes)，32 个引脚，长度为 39 毫米
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PCIe x8：有8 个通道(8 lanes)，49 个引脚，长度为 56 毫米
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PCIe x16：有16 个通道(16 lanes)，82 个引脚，长度为 89 毫米
PCI Express通道是主板芯片组与 PCIe 插槽(motherboard chipset and PCIe slots)或属于主板的其他设备之间的路径，例如处理器插槽(processor socket)、M.2 SSD插槽、网络适配器、SATA控制器或USB控制器。
在PCI Express中，每个通道都是独立的，这意味着它不能在不同设备之间共享。例如，如果您的显卡连接到PCIe x16 插槽(PCIe x16 slot)，则意味着它有 16 个独立通道专用于它。除了显卡，没有其他组件可以使用这些通道。
这里有一个想法可能会让您更容易掌握什么是PCI Express通道：想象一下PCI Express是一条高速公路，而在其上行驶的汽车就是正在传输的数据。高速公路上可用的车道越多，可以在上面行驶的汽车就越多；您拥有的PCIe(PCIe)通道越多，可以传输的数据就越多。
PCI Express 卡(PCI Express card)可以安装在主板上任何可用的PCIe 插槽(PCIe slot)上，只要该插槽不小于扩展卡(expansion card)即可。例如，您可以将PCIe x1 卡(PCIe x1 card)安装在PCIe x16 插槽(PCIe x16 slot)中。但是，你不能做相反的事情。例如，您可以在PCIe x16 插槽中安装(PCIe x16 slot)PCIe x1声卡，但不能在PCIe x1 插槽中安装(PCIe x1 slot)PCIe x16显卡。
有哪些PCI Express版本，它们支持哪些数据传输速度（带宽）？
目前使用(use today)的PCI Express有四个版本：PCI Express 1.0、PCI Express 2.0、PCI Express 3.0和PCI Express 4.0。每个 PCIe 版本支持的带宽大约是以前 PCIe 的两倍(Each PCIe version supports roughly double the bandwidth of the previous PCIe)。以下是他们每个人提供的内容：
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PCI Express 1.0：250 MB/s per lane的带宽为250 MB/s
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PCI Express 2.0：每个通道的带宽为500 MB/s per lane
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PCI Express 3.0：每通道的带宽为984.6 MB/s per lane
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PCI Express 4.0：每通道带宽为1969 MB/s per lane
还记得(Remember)PCIe 插槽(PCIe slot)不仅可以提供一个通道，还可以提供更多通道？我们共享的带宽值乘以PCIe 插槽(PCIe slot)上可用的通道数。如果要计算某个扩展卡(expansion card)有多少带宽可用，则必须将其每通道的PCIe 带宽(PCIe bandwidth)乘以可用的通道数。
例如，支持PCI Express 4.0并连接到PCIe x16 插槽的显卡可以获得大约 31.51 (PCIe x16 slot)GB/s的总带宽。这是1969 (multiplying 1969) MB/s乘以 16（每通道PCIe带宽lane * 16通道）的结果。令人印象深刻，对吧？
以下是考虑PCI Express通道时PCI Express版本的扩展方式：(PCI Express)
未来还会有新的PCI Express版本出现，例如PCI Express 5.0和PCI Express 6.0。PCIe 5.0规范已于 2019 年夏季敲定，每通道提供高达 3938 MB/s 的带宽，在MB/s配置下(x16 configuration)可提供高达 63 GB/s的带宽。但是，我们可能不会很快在消费级计算机硬件(computer hardware)上看到它。
最新的PCI Express 4.0是否广泛可用？
目前，PCI Express 4.0是适用于家用计算机的最快规范。然而，PCI Express 4.0 仅在 AMD 最新主板上受支持，这些主板基于 X570 芯片组与第三代 AMD Ryzen 处理器配对。(PCI Express 4.0 is only supported by AMD on its latest motherboards that are based on the X570 chipset paired with AMD Ryzen processors from the third generation.)除非你有这些，否则购买支持PCIe 4.0(PCIe 4.0)的显卡或固态硬盘是没有意义的。
说到这，虽然支持 PCIe 4.0的(support PCIe 4.0)SSD(SSDs)已经很多了，但唯一能在PCIe 4.0上工作的显卡是AMD的Radeon RX 5000s，比如Radeon RX 5700 XT 和 Radeon RX(XT and Radeon RX) 5700。英特尔(Intel)还没有提供支持适用于任何硬件上的PCI Express 4.0 。
PCI Express 4.0如何影响您的显卡速度？
有人在问一个有趣的问题：更快更新的PCI Express 4.0规范是否会对显卡的速度产生积极影响？快速回答是否定(no)的，它不会，而且您不会获得更多的每秒帧数！原因如下：
当您玩游戏时，显卡使用其专用RAM ( GDDR ) 来保存用于在屏幕上渲染帧的纹理。除了GPU时钟，图形内存对于你每秒获得多少帧是最重要的。
显卡仅在需要与处理器通信或从系统内存(system memory)（计算机的RAM ）加载纹理时，才需要使用将其连接到主板的(processor or load textures)PCI Express 接口(PCI Express interface)。这不应该经常发生，因为现代显卡有很多自己的专用RAM 。而且，即使/当它发生时，一旦纹理通过PCI Express 接口(PCI Express interface)从系统RAM传输并加载到图形卡的内存中，它们就会保留在那里。原因是图形内存比系统的RAM快很多倍。
目前可用的显卡都不需要PCI Express 4.0 x16插槽提供的全部带宽。如需更多信息，请阅读我们关于PCI Express 4.0(impact PCI Express 4.0)与PCI Express 3.0在当今台式计算机中的影响的分析：PCI Express 4 与 PCIe 3(vs PCIe 3)：是否有性能改进(performance improvement)？
PCI Express版本的兼容性如何？
所有PCI Express版本都相互兼容。例如，即使您将PCI Express 4.0显卡连接到仅支持PCI Express 3.0甚至 2.0 的主板，它也能正常工作。然而，PCI Express 接口(PCI Express interface)的带宽受到最小因素的限制。例如，如果您将PCI Express 4.0 SSD连接到仅支持PCI Express 3.0的主板，则该SSD可以在PCIe 3.0上运行。它无法访问 7.88 GB/s的带宽，而只能使用 3.94 GB/s，因此其最大理论速度减半。
您还有其他关于PCI Express的问题吗？
现在您应该对PCI Express(PCI Express)是什么有了更好的了解，并更多地了解不同类型的PCIe插槽、通道和版本。您还有其他问题需要我们回答吗？如果你这样做了，或者你有什么要添加到这篇文章中的，请不要犹豫，在下面发表评论。
What is PCI Express? Do PCIe lanes, slots, and versions matter?
PCI Exрress is a populаr tеchnology these days, and many are asking what it is, what it does, and why there's so mυch fuss about graphics cards, solid-state driνes, and motherboards that suppоrt PCI Express 4.0. In thiѕ article, we're goіng to answer these questions. We are also going to try to shed somе light on what PCIe laneѕ аre, what types of PCIe slots are there, and what's new in PCІ Expresѕ 4.0. If you're curious to learn more, read on:
What is PCI Express, and what does it stand for?
PCI Express stands for Peripheral Component Interconnect Express and represents a standard interface for connecting peripheral hardware to the motherboard on a computer. In other words, PCI Express, or PCIe abbreviated, is an interface that connects internal expansion cards such as graphics cards, sound cards, Ethernet and Wi-Fi adapters to the motherboard. Furthermore, PCI Express is also used to connect some types of solid-state drives that are usually very fast.
What types of PCI Express slots and sizes are there, and what to PCIe lanes mean?
To interconnect the expansion cards to the motherboard, PCI Express uses physical slots. The common PCI Express slots we see on motherboards are PCIe x1, PCIe x4, PCIe x8, and PCIe x16. The number that comes after the "x" letter tell us the physical dimensions of the PCI Express slot, which, in its turn, is determined by the number of pins on it. The higher the number, the longer the PCIe slot and the more pins that interconnect the expansion card to the slot.
Furthermore, the "x" number also tells you how many lanes are available in that expansion slot. Here's how the commonly used PCIe slots compare:
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PCIe x1: has 1 lane, 18 pins, and 25 mm in length
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PCIe x4: has 4 lanes, 32 pins, and 39 mm in length
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PCIe x8: has 8 lanes, 49 pins, and 56 mm in length
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PCIe x16: has 16 lanes, 82 pins, and 89 mm in length
PCI Express lanes are paths between the motherboard chipset and PCIe slots or other devices that are part of the motherboard, such as the processor socket, M.2 SSD slots, network adapters, SATA controllers, or USB controllers.
In PCI Express, each lane is individual, meaning that it cannot be shared between different devices. For example, if your graphics card is connected to a PCIe x16 slot, it means that it has 16 independent lanes dedicated just to it. No other component can use those lanes except the graphics card.
Here's an idea that might make it easier for you to grasp what PCI Express lanes are: just imagine that PCI Express is a highway and the cars that drive on it are the data that's being transferred. The more lanes you have available on a highway, the more cars that can drive on it; the more PCIe lanes you have, the more data that can be transferred.
A PCI Express card can fit and work on any PCIe slot available on the motherboard, as long as that slot is not smaller than the expansion card. For example, you can fit a PCIe x1 card in a PCIe x16 slot. However, you can't do the opposite. You can mount, for instance, a PCIe x1 sound card in a PCIe x16 slot, but you cannot mount a PCIe x16 graphics card in a PCIe x1 slot.
What PCI Express versions are there, and what data transfer speeds (bandwidth) do they support?
There are four versions of PCI Express in use today: PCI Express 1.0, PCI Express 2.0, PCI Express 3.0, and PCI Express 4.0. Each PCIe version supports roughly double the bandwidth of the previous PCIe. Here's what each of them offers:
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PCI Express 1.0: has a bandwidth of 250 MB/s per lane
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PCI Express 2.0: has a bandwidth of 500 MB/s per lane
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PCI Express 3.0: has a bandwidth of 984.6 MB/s per lane
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PCI Express 4.0: has a bandwidth of 1969 MB/s per lane
Remember that PCIe slots can offer not just one, but more lanes? The bandwidth values we shared are multiplied by the number of lanes available on a PCIe slot. If you want to calculate how much bandwidth is available for a certain expansion card, you have to multiply its PCIe bandwidth per lane with the number of lanes that are available for it.
For example, a graphics card that supports PCI Express 4.0 and is connected to a PCIe x16 slot has access to a total bandwidth of about 31.51 GB/s. That's the result of multiplying 1969 MB/s by 16 (PCIe bandwidth per lane * 16 lanes). Impressive, right?
Here's how PCI Express versions scale when you take PCI Express lanes into account:
In the future, there are new PCI Express versions coming, such as PCI Express 5.0 and PCI Express 6.0. The PCIe 5.0 specification has been finalized in the summer of 2019, offering a bandwidth of up to 3938 MB/s per lane and up to 63 GB/s in x16 configuration. However, we're likely not going to see it soon on consumer-grade computer hardware.
Is the latest PCI Express 4.0 widely available?
For now, PCI Express 4.0 is the fastest specification available for home computers. However, PCI Express 4.0 is only supported by AMD on its latest motherboards that are based on the X570 chipset paired with AMD Ryzen processors from the third generation. Unless you have these, there's no point in buying graphics cards or solid-state drives that support PCIe 4.0.
Speaking of which, although there are already many SSDs that support PCIe 4.0, the only graphics cards that do work on PCIe 4.0 are AMD's Radeon RX 5000s, such as Radeon RX 5700 XT and Radeon RX 5700. Intel has yet to offer support for PCI Express 4.0 on any of its hardware.
How does PCI Express 4.0 affect the speed of your graphics card?
Some people are asking an interesting question: Does the faster and newer PCI Express 4.0 specification positively affect the speed of the graphics card? The quick answer is no, it doesn't, and you do not get more frames per second! Here's why:
When you are playing a game, the graphics card uses its dedicated RAM (GDDR) to hold the textures used for rendering the frames on the screen. Besides the GPU clocks, that graphics memory is the most important thing for how many frames you get each second.
The graphics card only has to use the PCI Express interface that connects it to the motherboard when it needs to communicate with the processor or load textures from the system memory (the computer's RAM). That's not supposed to happen often, as modern graphics cards have a lot of dedicated RAM of their own. And, even if/when it happens, once the textures have been transferred via the PCI Express interface from the system RAM and have been loaded into the graphics card's memory, they stay there. The reason for that is that the graphics memory is many times faster than the system's RAM.
None of the graphics cards available today need the full bandwidth offered by the PCI Express 4.0 x16 slots. For further information, read our analysis about the impact PCI Express 4.0 has versus PCI Express 3.0 in today's desktop computers: PCI Express 4 vs PCIe 3: Is there a performance improvement?
What about PCI Express versions compatibility?
All PCI Express versions are compatible with one another. For example, a PCI Express 4.0 graphics card works even if you connect it to a motherboard that only supports PCI Express 3.0 or even 2.0. However, the bandwidth of the PCI Express interface is limited by the smallest factor. For example, if you connect a PCI Express 4.0 SSD to a motherboard that only supports PCI Express 3.0, that SSD works on PCIe 3.0. Instead of having access to a bandwidth of 7.88 GB/s, it can only use 3.94 GB/s, so its maximum theoretical speed is halved.
Do you have any other questions regarding PCI Express?
Now you should have a better idea of what PCI Express is, and understand more about the different types of PCIe slots, lanes, and versions. Do you have any other questions that we might answer? If you do, or if you have something to add to this article, do not hesitate to leave a comment below.
