One of the features found on the most recent CPUs, chipsets, motherboards, and video cards is the PCI Express 3.0 connection. Nevertheless, does it offer an actual performance improvement over the PCI Express 2.0 standard? Let’s find out!
PCI Express 3.0 connection was specified in 2010, with a maximum theoretical transfer rate per lane of almost 1 GiB/s (actually, 984.6 MiB/s), twice the rate of the PCI Express 2.0 standard that offers 500 GiB/s per lane. Thus, a PCI Express 2.0 x16 slot offers a maximum theoretical bandwidth of 8 GiB/s, while a PCI Express 3.0 x16 slot reaches 16 GiB/s.
Let us keep in mind that those are the maximum speeds this connection supports, which does not mean the video card will transfer data at these speeds. For more detailed technical information, read our “Everything you need to know about the PCI Express” tutorial.
Regarding to video cards, all current models are compatible with PCI Express 3.0; the first NVIDIA chips compatible with this standard were from GeForce GT/GTX 6xx generation, while the AMD models use it since Radeon HD 7xxx models.
On the other side, in most cases, is the CPU that supports PCI Express 3.0, not the chipset. However, it is necessary the motherboard also to be compatible with the standard. Intel CPUs support PCI Express 3.0 since the third generation Core i (“Ivy Bridge”) processors. AMD A-series CPUs (aka APUs) support the standard on all FM2+ models. FX processors, on the other hand, do not support PCI Express 3.0, because on this platform, the PCI Express lanes are generated by the chipset, and even the most high-end model, 990FX, supports only PCI Express 2.0.
Besides the big difference on the maximum theoretical bandwidth between the CPU and GPU, we were still curious about the real-life performance impact on games by using a PCI Express 3.0 against a 2.0 connection. So, we ran 3D benchmarks using 3DMark and some recent games, using a high-end video card (which, in theory, demands more bandwidth than a mainstream or value one), first with the slot configured as PCI Express 3.0 x16, then with the same slot configured as PCI Express 2.0 x16. Finally, we tested with the same video card, but this time using a slot that supports up to PCI Express 3.0 x4, to check if an ever lower bandwidth could affect performance.
Figures 1, 2, and 3 show the configuration of the video card slot, on the “Bus Interface” field at GPU-Z screen.
Figure 1: using PCI Express 3.0 x16
Figure 2: using PCI Express 2.0 x16
Figure 3: using PCI Express 3.0 x4
We will list the configuration we used on our tests on the next page.