PCIe Bandwidth & Slots

Every Xtreme card states a PCIe generation and lane count (e.g. "8-lane PCIe Gen.3") and a maximum data rate. Two things determine whether a card will actually hit that number in your system: how many lanes the physical slot provides, and which PCIe generation the slot and card both support — a Gen.3 card in a Gen.2 slot will still work, but is capped at Gen.2 bandwidth.

This matters most in VSN chassis with a mix of capture and graphics cards competing for backplane bandwidth. Our Express9-G3 and Express11-G3 backplanes use PCIe 3.0 switching to give every slot up to 8GB/s bidirectional bandwidth — as a rough guide, that's enough headroom for around 14 full HD streams at 60Hz/32bpp in either direction between chassis, which is why the -G3 backplanes are worth specifying even with older Gen.1/Gen.2-rated cards if you're daisy-chaining an expansion chassis.

If a wall is dropping frames or showing tearing on specific channels, checking whether the relevant card is seated in a full-bandwidth slot — rather than a lane-limited one further down the backplane — is one of the first things our support team checks.

Still deciding between a PCIe chassis and a standalone controller? See PCIe vs USB capture cards, or choosing a VSN chassis for slot-count guidance.