If you wanted nothing but ultimate performance in games, CrossFire and SLI were the only options for a long time. DirectX 12 was intended to offer an alternative, but it doesn't seem to be the promised holy land for multi-GPU setups. That is why it is high time to take stock: is the combination of several video cards still relevant in 2018, or does the fairy tale of CrossFire and SLI have an unhappy ending?
To make a good judgment of CrossFire and SLI in the present day, we have had dual-GPU configurations of the top models from both camps go through our full 3D chip test. That's the same test we use to test a new GPU at launch. We went through the entire test course with both the AMD Radeon RX Vega 64 in CrossFire and the Nvidia GeForce GTX 1080 Ti in SLI.
On the next page we will take a closer look at the current technology behind CrossFire and SLI, but first we will look at it in general: what do you need to combine several video cards? AMD differs from Nvidia, as one would expect from the two rivals. The latest AMD graphics cards, including those based on the Polaris and Vega GPU, use XDMA. This no longer involves the use of a physical bridge, but the mutual communication simply takes place via the PCI Express port. With the introduction of Pascal, Nvidia switched to a faster type of SLI bridge, the so-called HB-SLI-bridge. Various manufacturers are producing such bridges, which cost a few tens of euro.