TECH REPORT
Whatever happened to MULTI-GPU setups?
“This is the way the world ends”, wrote TS Eliot in his 1925 poem The Hollow Men.
“Not with a bang but a whimper.” It’s hard to say if Eliot was writing directly about Nvidia and AMD’s support for multi-GPU setups or speaking more allegorically.
Perhaps we’ll never know. What we can all roundly agree on is that Eliot lands on a truism when it comes to technology in general: there’s never an announcement. Yesterday’s Next Big Thing is instead quietly escorted out of the building and stuffed into a bin away from prying eyes.
We didn’t get any press releases confirming the formal demise of 3D TVs in the mid-2010s, we’ll get no such PR when VR dies in 2030 (fight me), and neither SLI nor Crossfire got the official state funerals they deserved when, at some point in the last five years, multi-GPU PC builds simply stopped being a thing.
The concept is an old one. Even in the days before 3DFX was the last word in PC gaming graphics hardware, before the Nvidia buyout, the company behind Voodoo was finding ways to run two of its cards in parallel. Voodoo 2 introduced scan-line interleave (SLI) support in February 1998. For context, that’s three months before Unreal came out, and only a few weeks after the discovery of penicillin.
To the consumer, it worked just like later iterations of SLI and Crossfire did: you placed two identical graphics cards in your motherboard’s PCI slots, and connected them with a proprietary ribbon cable. That enabled your two Voodoo 2s to process graphical rendering tasks in parallel for faster performance. That was the theory.
EARLY PROBLEMS
But the problems for 3DFX’s early SLI were the same ones that ultimately spelled the end for multi-GPU gaming three decades later. The biggie: games didn’t automatically recognise that you had two graphics cards available, and they didn’t know how to make use of all that extra bandwidth.
To make that happen, game developers needed to write code specifically to make use of two graphics cards running in parallel. And that provoked the usual chicken-egg conundrum that befalls so many pioneering technologies: without a large enough user base demanding SLI support, there wasn’t much incentive on developers to spend more time and money writing the code to support and optimise it. And without the games to support it, there wasn’t much consumer uptake on SLI. See also: VR. (I mean it, come and fight me.)
Two’s a crowd
In addition to the technology that allowed multiple discrete cards to be linked together, all the big stakeholders in PC graphics also began to design multi-GPU circuits on a single card. Even the humble 3DFX Voodoo 2 featured three separate cores, although this wasn’t
