▷ Pci express 3.0 vs pci express 2.0

One of the features found in today's CPUs, chipsets, motherboards, and graphics cards is the PCI Express 3.0 connection. However, what is the difference from the previous PCI Express 2.0 standard? Let's find out! PCI Express 3.0 vs PCI Express 2.0.

PCI Express 3.0 vs PCI Express 2.0, differences in specifications

PCI-SIG announced the availability of the PCI Express Base 2.0 specification on January 15, 2007. The PCIe 2.0 standard doubles the transfer rate compared to PCIe 1.0 at 5GB / s and throughput per lane increases from 250MB / s to 500MB / s. The PCIe 2.0 motherboard slots are fully compatible with PCIe v1.x cards. PCIe 2.0 cards are also generally compatible with PCIe 1.x motherboards, using the available bandwidth of PCI Express 1.1. In general, graphics cards or motherboards designed for v2.0 will work with the other v1.1 or v1.0a.

The PCI-SIG also said that PCIe 2.0 features improvements to the point-to-point data transfer protocol and its software architecture. Intel's first PCIe 2.0-capable chipset was the X38, and boards began shipping from multiple vendors (Abit, Asus, Gigabyte) beginning October 21, 2007. AMD began supporting PCIe 2.0 with its AMD 700 series of chipsets. and Nvidia started with the MCP72. All previous Intel chipsets, including the Intel P35 chipset, supported PCIe 1.1 or 1.0a.

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The PCI Express 3.0 connection was specified in 2010, with a maximum theoretical transfer rate per lane of almost 1 GB / s (actually 984.6 MB / s), double the rate of the PCI Express 2.0 standard offering 500 GB / s per lane. Therefore, a PCI Express 2.0 x16 slot offers a theoretical maximum bandwidth of 8 GB / s, while a PCI Express 3.0 x16 slot reaches 16 GB / s. PCI Express 3.0 updates the encryption scheme to 128b / 130b from the previous 8b / 10b encryption, reducing the bandwidth overhead of 20% of PCI Express 2.0 to approximately 1.54% (= 2/130).

A desirable balance of 0 and 1 bits in the data stream is achieved by XORing a binary polynomial known as a "scrambler" of the data stream in a feedback topology. Because the randomization polynomial is known, the data can be retrieved by applying the XOR a second time. The scrambling and decoding steps are done in hardware. The 8 GT / s bit rate of PCI Express 3.0 offers 985 MB / s per lane, which doubles the bandwidth of the lane compared to PCI Express 2.0.

PCI Express 3.0 vs. PCI Express 2.0 Does it affect gaming performance?

Keep in mind that those are the maximum speeds that this connection supports, which does not mean that the video card transfers data at these speeds. Regarding graphics cards, all current models are compatible with PCI Express 3.0. The first Nvidia chips compatible with this standard were from the GeForce GT / GTX 6xx generation, while AMD models use it from the Radeon HD 7xxx models.

On the other hand, in most cases, it will be the CPU that includes the PCI Express 3.0 interface, not the chipset. However, it is necessary that the motherboard also supports the standard. Intel CPUs support PCI Express 3.0 from the third generation of Core i ("Ivy Bridge") processors. AMD CPUs are standard compliant on all FM2 + and AM4 models. On the other hand, FX processors are not compatible with PCI Express 3.0, since on this platform, PCI Express circuits are generated by the chipset, and even the most advanced model, 990FX, only supports PCI Express 2.0.

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In addition to the huge difference in theoretical maximum bandwidth between CPU and GPU, we are curious about the real-life performance impact of gaming when using a PCI Express 3.0 against a 2.0 connection. So, we have used tests using a high-end GeForce GTX 980Ti video card, first with the slot configured as PCI Express 3.0 x16 and then with the same slot configured as PCI Express 2.0 x16.

GeForce GTX 980 Ti	PCI Express 2.0	PCI Express 3.0
Battlefield 4	189 FPS	187 FPS
Dirt Rally	173 FPS	173 FPS
Dying Light	115 FPS	123 FPS
Grand Theft Auto V	138 FPS	143 FPS
Mad Max	149 FPS	149 FPS

The tests show a clear result, because of all the games tested, only in the case of Dying Light was there a significant increase in performance when using PCI Express 3.0 instead of PCI Express 2.0. Even so, the improvement was only 7%, a very low figure. Remember that a high-end video card has been used in a high-end system. If the tests had been run on a more basic system, it stands to reason that, on a system with lower graphics card performance, the impact of bandwidth between the two generations of PCI Express should be even less.

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