PCIe 3.0 vs PCIe 2.0 is a common question for gamers and PC users looking to either upgrade their system or bring home a new PC. Apart from the bandwidth and age, there’s not much difference between the two. The primary difference in subsequent versions for any hardware is the bandwidth (or speeds), like in the case of USB 2.0 and USB 3.0.
The PCIe (Peripheral Component Interconnect-Express) bus is the current generation of high-speed expansion technology that is used in various personal computer (PC) platforms or motherboards, to enable devices such as graphic cards or network interface cards to communicate with other PC components at a higher speed and using less CPU (central processing unit) resources.
In this article, we have explained the differences and similarities between PCIe 3.0 vs PCIe 2.0 in 2023.
Understanding PCIe Lanes
The technology behind the PCIe slots on our PCs is way more extensive than it appears. It is, also, one of the most essential requirements of building a PC. PCIe Lanes help provide a physical link between the devices and the processor or motherboard. Traces, the two pairs of Copper Wires, run through the motherboard PCB. They connect the PCIe-enabled devices to the processor or motherboard chipset.
A single PCIe lane provides a bi-directional flow of data, like a two-way highway. For higher bandwidth, and reducing the latency of data, up to 32 lanes can be allotted for each device. Consumer PCs usually come with up to 16-lane support, and PCs have support for up to 32 lanes. The bandwidth range is as follows:
| PCIe Lanes | Bandwidth |
| X1 | 2.5Gbps/200Mbps (Single Direction) 5Gbps/400Mbps (Both Directions) |
| X4 | 10Gbps/800Mbps (Single Direction) 20Gbps/1.6Gbps (Both Directions) |
| X8 | 20Gbps/1.6Gbps (Single Direction) 40Gbps/3.2Gbps (Both Directions) |
| X16 | 40Gbps/3.2Gbps (Single Direction) 80Gbps/6.4Gbps (Both Directions) |
Also, read the Samsung 870 Evo Vs 860 Evo SSD Comparison.
PCIe Versions, Lanes, And Throughputs
The speeds/throughputs of various PCIe versions on different PCIe Lanes are summarized below:
| Version | X1 | X2 | X4 | X8 | X16 |
| 1.0 | 0.25 | 0.5 | 1 | 2 | 4 |
| 2.0 | .5 | 1 | 2 | 4 | 8 |
| 3.0 | .985 | 1.969 | 3.938 | 7.877 | 15.754 |
| 4.0 | 1.969 | 3.938 | 7.877 | 15.754 | 31.508 |
| 5.0 | 3.938 | 7.877 | 15.754 | 31.508 | 63.015 |
| 6.0 | 7.877 | 15.754 | 31.508 | 63.015 | 126.031 |
The version and slot have larger applications to design better computer systems. For example, an x16 PCIe 2.0 slot and an x8 PCIe 3.0 slot can deliver the same performance. The lesser number of slots for the same performance helps build more efficient smaller systems, while also opening up PCIe lanes for further usage.
It can even come down to smaller heat sinks and capacitors. Heat is one of the primary reasons for the lower and less efficient performance of computers. The smaller the components, the lesser the heat, and the higher the efficiency of the system. Even the depreciation of performance will be exponentially smaller with more efficient systems.
Both the manufacturers and the consumers gain through this, hence pushing for better systems that drive a more efficient PC market.
Similarities Between PCIe 3.0 vs 2.0
PCIe 3.0 and PCIe 2.0 are different generations of the same component. They are similar in the way they function, and their physical appearance. The size and shape of the PCIe slots are the same across generations. Thus, x1 and x16 slots of both PCIe 3.0 and PCIe 2.0 are the same.
The similarities in the size and shape point to cross-usability. Thus, a PCIe 3.0 slot can be used for a PCIe 2.0 component, and vice versa. Although not ideal, this similarity is helpful when working with backup components temporarily. Ideally, one would never use the wrong generation component because of performance sacrifice.
An older motherboard with PCIe 2.0 slots can run a PCIe 3.0 expansion device. The device will, though, work at the speed of the lower-power device or slot. Thus, the PCIe 3.0 device will run at its PCIe 2.0 device speed. This is called a bottleneck, where the maximum capability of a device isn’t used because of a lack of resources on the hardware part of the motherboard.
Similarly, a PCIe 2.0 device will work smoothly and at its maximum speed on a PCIe 3.0 slot. However, the slot can deliver much higher speeds, and thus there’s an under-utilization of the resources at hand.
Differences Between PCIe 3.0 vs 2.0
PCIe 3.0 is the next generation of the PCIe, after PCIe 2.0. Naturally, there are plenty of differences between the two. Some of them are listed below:
1) PCIe Lane Speeds
The classic formula that each subsequent PCIe generation doubles the speed stands ground with the PCIe 3.0. It offers a bandwidth starting at 0.985 GB/s (almost 1), as opposed to the 0.5 GB/s bandwidth of the PCIe 2.0 slot. Wider data lanes and an advanced coding system are the primary reasons for the upgrade of performance, apart from the overall upgraded technology of the devices created for the PCIe 3.0 slot.
2) Device Size And Speed Impact
Since the speeds are doubled, the sizes are effectively halved. The performance of a graphics card, designed to work on 16 PCIe 2.0 lanes would work the same on 8 PCIe 2.0 lanes. Thus, you either save slots, or you can have fewer slots and a more compact cabinet.
3) The More Efficient Encoding System
The subsequent generations of PCIe are also more efficient. The PCIe 2.0 uses an 8b/10b encoding system, where 8 bits of every 10 bits transmitted are data, while the remaining 2 bits are the overheads (20% overheads). The encoding system for PCIe 3.0 is 128b/130b, resulting in 1.5% overheads, with 2-bit overheads and 128-bit data out of 130-bit transmission.
The reduced transfer overheads help in achieving a higher maximum bandwidth, which is double in PCIe 3.0 vs PCIe 2.0. A better encoding system means that the actual transfer rate isn’t doubled while doubling the bandwidth.
4) Efficiency In Power Use
Since the overall cabinet, heat is dependent on the size of the components, and thus the resulting requirement of cooling solutions, a more efficient system helps reduce power use through smaller equipment delivering the same power as its previous generation. This also results in cheaper expansion components of the PC, as compared to the previous generations. This is how the smaller cabinet sizes are delivering great power these days.
5) A Case For Longer Usage
When the expansion cards in PCIe slots are smaller, the cooling systems and fans are also smaller, thus making long-term usage easier. The overall system temperature is also easier to maintain. A more efficient system helps prolong the life of the overall hardware components. Thus, apart from preventing bottlenecks, upgrading the complete system to a PCIe 3.0 slot motherboard and PCIe 3.0 expansion slots is a much better option than to continue using older components, especially if you are looking to upgrade at least one component.
Conclusion
PCIe 3.0 vs PCIe 2.0 isn’t merely a generational change. Owing to its similarities, the PCIe slots work as a bridge between the generations. More efficient computer systems can be produced by the next generation of PCIe, affecting the entire ecosystem of the PC market. Smaller, cooler, and faster PCs with higher durability come as a part of the bargain as you make a switch to PCIe 3.0.
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