PCI Express Generation 1 vs. Generation 2 vs. Generation 3 vs. Generation 4

PCI Express (Peripheral Component Interconnect Express) often knows by the name PCI-E and it is a standard form of connection that is established among the internal devices in any computer system.

On the usual terms, the PCI Express is generally used for representing the actual expansion slots that are present on the motherboard which accepts the PCIe-based expansion cards and to several types of expansion cards themselves.

The computer systems might contain several types of expansion slots, PCI Express is still considered to be the standard device for establishing the connection between various internal devices.



#Different Slots of PCI Express

You would come across various slots of the PCI Express including PCI Express x1, PCI Express x4, PCI Express x8, and PCI Express x16 ( in under all PCIe generations).

Though, several users are confused about the exact meaning of “x” in PCI Express Slots, how to tell which type of slot would support the particular hardware, what options are available and so more.

X mainly refer for multiplying, we count PCI Express Slot’s bandwidth by a term called ‘PCIe Lane’. The size of PCIe Slot chiefly depends upon how much PCIe lanes it can provide. That’s why a single lane x1 Slot is smaller than the 16 Lanes x16 Slot.

PCIe Slots are backward compatible like most of the interfaces, which means that you can use any generation card on any generation slot. But it’s quite possible that the newer generation card will bottleneck with the old generation slot. The bandwidth speed gets doubled over each generation. Newer generation lane is twice as fast as the previous one. 

There is one more thing, you can use any PCIe Express Card in any PCI Express Slot. Which means if your computer motherboard has an open x1 Slot as shown in the example picture, then you can install any x4, x8 or even a x16 Graphics Card into the x1 PCIe Slot. The expansion card will work just fine, but the speed of communication is limited to the single lane.

If the smaller size slot is closed at the end like in most of the motherboards, then you can easily make a space by using a hand saw or a blade.

There is also a small version of PCIe x1 Slot available on the desktop or laptop motherboard called ‘Mini-PCIe Slot’. Because of the 180° card installation compatibility, you can mostly find this slot on laptops. As it’s the shorter variant of x1, Mini-PCIe only contains a single Lane bus, but the bandwidth speed can vary according to the PCIe generation of your motherboard.

However, once the users have understood the important aspects and major differences among each format and PCI Express version, then it becomes all easy to realize the difference.

#So, Now Let’s Start With PCI Express Versions

During the early stages of development, the PCI Express was initially known as “High-Speed Interconnect” (HSI). From various changes in its name like 3GIO (3rd Generation Input/Output) and PCI-SIG finally settled for the name PCI Express.

PCI Express is a form of technology that is always under some sort of technical modifications. Here are some of the basic versions of the PCI Express that have been used in the computer systems for their high performance and efficiency parameters:

  • PCI Express 1: It was in 2005 that PCI-SIG had introduced the PCI Express 1 version. This was an updated version of the previous PCI Express 1.0a (launched in 2003) that came with several improvements and clarifications.
  • PCI Express 2: PCI-SIG had announced the availability of the PCI Express 2.0 version in 2007 that came with doubled transfer rate in comparison to the PCI Express 1 version. The per-lane throughout was increased from 250 MBps to 500 MBps. The PCI Express 2.0 motherboard is entirely backward compatible with the presence of PCI Express v1.x The PCI-SIG also claimed several improvements in the feature list of PCI Express 2.0 from point-to-point data transfer protocol along with the software architecture.
  • PCI Express 3: It was in 2007 that PCI-SIG had announced that the version of PCI Express 3.0 would be offering a bit rate of 8 Giga-transfers per second (GT/s). Moreover, it was also supposed to be backward compatible with the current implementations of the existing PCI Express PCI Express 3.0 came with an upgraded encoding scheme to around 128b/130b from the previous encoding scheme of 8b/10b.
  • PCI Express 4: PCI-SIG officially announced PCI Express 4.0 on June 8, 2017. There are no encoding changes from 3.0 to 4.0. But when it comes to the performance, PCIe 4.0 throughput per lane 1969 MB/s.
  • PCI Express 5: Expected in late 2019 and as usual the speed will also be going to get double.




#PCI Express Versions: 1.0 vs. 2.0 vs. 3.0 vs. 4.0

Unlikely RAM’s Slot, you actually can’t tell the difference between PCIe Slot generations by just looking at it. On some motherboards, it’s written on the PCB but generally, you won’t find it until you check your motherboard’s specification online or on the box.

PCIe Versions bandwidth comparison chart:

In addition to this, each latest version of the PCI Express comes with additional improved specifications and functional performance.

For instance, PCI Express 2.0 version comes with doubled transfer rate than of the previous PCI Express 1.0 version. It also comes with improved per-lane throughput from 250 Mbps to 500 Mbps.

Similarly, PCI Express 3.0 comes with an upgraded encoding scheme of 128b/130b from the previous 8b/10b encoding scheme. It, therefore, reduces the bandwidth overhead from around 20 percent of the previous PCI Express 2.0 version to a mere of around 1.38 percent in PCI Express 3.0. This major improvement has been achieved by a technical process referred to as “scrambling”.

The process of scrambling makes use of a recognized binary polynomial to a particular data stream in the feedback topology. As the scrambling polynomial is recognized, therefore, the data is able to be recovered by running the same through a particular feedback topology which makes use of the inverse polynomial.

In addition to this, the 8 GT/s bit rate of the PCI Express 3.0 version also delivers 985 MBps per lane effectively. This tends to practically double the overall lane bandwidth in comparison to the older versions of PCI Express 2.0 and PCI Express 1.0.

All of the PCI Express versions are both forward as well as backward compatible. This implies that irrespective of the particular version of the PCI Express your computer system or motherboard is able to support, they should be working together, at least at some minimum level.

As one can observe that the major updates to different versions of the PCI Express have increased the overall bandwidth drastically each time. Therefore, this feature greatly increases the potential of what the particular connected hardware is able to do.

As a result, the overall performance of the computer system in coordination with the different hardware components gets enhanced.

In addition to the overall performance enhancements, the update to different versions of the PCI Express also tend to bring about effective bug fixes, additional technical features, and improved power management.

On top of it all, the improvement in the bandwidth is the most significant change that is brought about by any update of the PCI Express version.

#Maximizing PCI Express Compatibility

If you wish to get the highest bandwidth for faster data transfers and overall improved performance, then you would want to select the highest PCI Express version that would be supported by the motherboard along with the largest PCI Express size that would fit in the same.

>> Suggested Link: PCI Express (PCIe) – Everything You Need To Know

“And that’s all for now, thanks for sticking with the article, and you know it will always good to let me know about the article, in the comments down below.” 🙂


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