PCIE Generation Differences explained

The Differences in Generational PCIe slots

With PCIe Gen 3.0, processors and compatible platforms (mobo and VGA) can feature 16 PCIe 3.0 lanes to be used for graphics and/or other add-in PCI cards. The all new PCI Express Gen 3 is really fantastic, but what does that mean to you as an end user ??

Simply put, PCI Express Gen 3 provides a 2X faster transfer rate (bandwidth) over the previous 2.0 generation, this delivers capabilities for next generation gaming graphics cards. PCI Express Gen 3 actually has twice the available bandwidth, 32 GB/s per lane (bi-directional), but also some efficiency and compatibility. It is the best performing and functional PCIE Slot for today's PCI Express cards such as graphics cards. Moving from PCIe Gen 2 to Gen 3 doubles the bandwidth available to the add-on cards installed, from 500 MB/s per lane to 1 GB/s per lane. So a Gen 3.0 PCI Express x16 slot is capable of offering 16 GB/s of bandwidth in each direction. In total that sums up towards a whopping 32 GB/sec bi-directional bandwidth. Obviously the hardware you use needs to be Gen 3.0 compatible. PCI Express is a bi-directional point-to-point link, so it offers the same bandwidth in both directions and does not share its bandwidth with other devices. Example 20 PCI Express lanes can be arranged as one x16 PCIe slot and four x1 PCIe slots, which is also common practice with many chipsets. The processor we use today for example has 40 PCIe Lanes available, meaning we can mount two x16 Gen 3.0 graphics cards and we'd still have bandwidth to spare.

Put very simple:

• PCI-Express 1.1 sends 250 MB/s per direction
• PCI-Express 2.0 sends 500 MB/s per direction
• PCI-Express 3.0 brings that number towards a whopping 1 GB/s.

So that new Gen 3.0 x16 slot of yours can handle a total bandwidth of 32 GB/s (bi-directional) in PCIe Gen 3.0 mode, whereas the old Gen 1.0 x16 slot would be capable of 8GB/sec (bi-directional).

Will that last bandwidth limited slot have an impact on your gaming performance with say a modern age GeForce GTX 980 ? Well that is what we are going to try and find out today, with both a single card and a second one setup in SLI.