Multi GPU Technology - How Does Lucid's Hydra Chip Work?
A Multi-GPU Revolution?
Over a year ago a company named Lucid showed up at the Intel Developer Forum with an interesting new technology. They claimed to be in development of a chip which allowed multiple GPUs to work together. ATI and Nvidia have, of course, had their own versions of this for years, but what made Lucid’s implementation unique was that the chip was supposed to work no matter which video cards were involved. In other words, one would be able to combine cards of a different model, or even cards of a different brand, and use them together. They even claimed that their technology, which they called the Hydra chip, would be able to achieve nearly linear scaling, which is to say that as more GPUs were added the Hydra chip would allow them to perform to nearly 100% of their maximum potential. By contrast, both SLI and CrossfireX see diminishing returns as more cards are added.
As is often the case with these things, everyone reported on Lucid’s promises, and then the company promptly fell off the face of the earth. I know, as I was at their website constantly for updates. After months of apparent inactivity I decided that Lucid had bitten off more than it could chew.
Oh Me of Little Faith…
It was easy to dismiss Lucid’s claim. Hardware and software companies are constantly emerging with wild new claims, and they very often fail to achieve their goals. Creating new technology is difficult, as is finding people willing to place a bet on unproven technology. To Lucid’s credit, however, the company had already gained backing from someone who knows quite a bit about computer technology - Intel. They debuted their technology at the Intel Developer Forum because Intel is their primary backer.
Lucid came back in the spotlight at this year’s Intel Developer Forum, where Lucid again showed off their technology. But this time they had more. Lucid unveiled that they had formed a partnership with MSI and that the new MSI Big Bang motherboard, to be released sometime in late October 2009, would be the first motherboard to feature Lucid’s Hydra chip. In other words, the Hydra chip is no longer vaporware.
How Does It Work?
Generally speaking, SLI and CrossfireX work by dividing a frame up into portions and rendering each portion on a separate card or by alternating the rendering load between cards. These are reasonably efficient methods, but its easy to see why they don’t allow for compatibility between different models or brands. If one were to pair a Radeon 5870 with a Radeon 4870, split a frame up, and then give one half to each card, the Radeon 5870 would be done first. The Radeon 5870 would therefor be limited by what the Radeon 4870 could do.
Lucid’s Hydra chip works differently. Instead of simply splitting frames into portions, it intercepts API calls, takes a look at them, and organizes them in the way it best sees fit. Then it distributes that information evenly across the GPUs in the system. In other words, the Hydra chip is actually intercepting the data that normally goes to the GPU and its driver and re-distributing that data for maximum efficiency. Lucid has proven this technology works by displaying the work done by two different GPUs on two different monitors. The image rendered was changing dynamically from frame to frame based on how the Hydra felt the information should be most efficiently rendered. Of course, the chip would normally recombine that information into one image which would then be displayed.
What is incredible about this technology, besides the fact that it allows GPUs of any model or brand to work together, is that it should allow for any number of GPUs to work together. This includes not only quad-GPU setups, which are the current maximum supported by motherboards, but also tens or even hundreds of GPUs working in tandem. Intel’s interest in Lucid may be tied to Intel’s graphics card project, Larrabee, which uses large numbers of processors on one card.
Coming to a PC Near You
Lucid isn’t out of the woods yet. The technology the Hydra chip uses could result in a lot of driver issues. That said, the potential is impressive. And although I am a born skeptic, the fact that Lucid has the backing of Intel and is going to be shipping an actual chip on a high-end motherboard made by MSI gives an indication that major players in the industry have seen this technology in action and decided it was valid enough to take a risk on.
It is hard to tell what the future holds, but it is always nice when we don’t have to wait long to find out.
