Dual GPUs Explained: Are Two Graphics Cards Better Than One?
Will two graphics cards offer enough of a performance upgrade to make such an expensive concept worth exploring? It's a complicated process that has an astounding number of potential caveats and side effects, but running dual graphics cards also means a clear performance upgrade. Before committing one way or the other, there's a lot of leg work to be done, and even after doing the research, you'll need some luck.
The appeal of instaling two graphics cards is as straightforward as it sounds. The raw specs of a graphics card – things like bandwidth and RAM – would absolutely be increased by adding a second card. That means it's possible to install two Nvidia GTX 1080 Ti GPUs and each would have a bandwidth of 484 GB/s: that card's standard bandwidth. If all things go according to plan, the dual-card setup will result in higher framerates and a higher ceiling for visual settings. There's also the added benefit that a two-card setup means it's possible to get more performance by just adding a card rather than entirely replacing one.
The initial complications come from the allocation of those resources, however. Installing two cards with 484 GB/s bandwidth doesn't translate to a GPU with and bandwidth of 968 GB/s. Part of the problem stems from how software interacts with a two-card setup. Nvidia GPUs will require that the motherboard is SLI-compatible and AMD cards will need a board that supports Crossfire. These technologies are necessary for a system to use both cards simultaneously to produce a single output. However, SLI and Crossfire don't always work exactly as they should, and even if the system is fine, certain software can malfunction or flat-out be incompatible with them. As a gamer, the viability of your entire PC setup would be subject to the whims of a title's developers.
The other side of the issue with running two graphics cards is obvious, but rarely gets the attention it should. Space is a huge concern when installing a second card. You'll need a motherboard with an appropriate number of PCIe slots, sure, but you'll also need enough clearance inside the chassis to support these GPUs which continue to increase in size. And, that's not just physical space, but also space for heat. Two GPUs can easily generate twice as much heat inside a chassis and can cause other components, like the CPU, to work harder, further increasing temperature concerns. This can be addressed with changes to your heat sink, but that's yet another layer of complication and a potential point of failure.
At multiple points, it's clear that having two GPUs can be a problem. The added power, while not quite double, is still beneficial in some ways, and adding a second GPU makes dual-monitor setups much easier. However, comparable performance is also achievable by purchasing a single, high-end card as well, and that performance is less likely to take a hit from SLI/Crossfire or a game that doesn't properly support them. For people who don't have incredibly intense editing demands or a multi-monitor setup, using two graphics cards is difficult to recommend.