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Hands on with Lucid's Hydra GPU load balancer

The first performance results revealed

Ever since its auspicious debut as a technology demo at last year's fall IDF, Lucid's Hydra chip has been an object of curiosity for us. Could this small start-up firm really create a GPU load-balancing chip that would function as smoothly as SLI and CrossFire, yet allow more leeway in mixing GPUs of different types? They'd taken on a daunting challenge, but they seemed to have a pretty good start on the problem.

Now, a little more than a year after that first IDF showing, Lucid says its Hydra 200 chip is ready to ship in consumer systems. To underscore that point, the firm recently invited us to its San Jose, California offices to experience a Hyrda-based solution first-hand. We came away with our impressions of the Hydra solution in action, along with some of the first performance numbers to be released to the public.

If you're unfamiliar with the Hydra, I suggest you read our original coverage of the chip, which introduces the basics pretty well. The basic concept is that the Hydra chip can sit on a motherboard, between the north bridge (or CPU) and the PCI Express graphics slots, and provide real-time load-balancing between two or more GPUs. The Hydra accomplishes this task by intercepting calls from a graphics API like DirectX, dynamically dividing up the workload, and then assigning a portion of the work required to draw each frame to each GPU. The Hydra then combines the results into a single, hopefully coherent image, which is then sent to the display.

Several things have changed over the past year, as the Hydra has moved from a technology demo toward a real product with proper driver software. Most notably, perhaps, the first Hydra silicon demoed supported only the PCIe Gen1 standard, whereas today's Hydra 200 series is PCIe Gen2-compliant.

In fact, the Hydra can support up to 48 lanes of PCIe 2.0 connectivity, with 16 "upstream" lanes to the host north bridge or CPU and 32 lanes intended for graphics cards. Those 32 lanes can be bifurcated into as many as four PCIe x8 connections, with several other configurations possible, including dual x16 connections and a single x16 plus dual x8s. The chip can auto-configure its PCIe connections to fit the situation, so this full range of connectivity options can be exposed on a single motherboard with the proper electrical connections and slot configuration.

The tiny Hydra chip package perched atop a holding case

To execute Lucid's load-balancing algorithms, the Hyrda chip also includes a 300MHz RISC core based on the Tensilica Diamond architecture, complete with 64K of instruction memory and 32K of data memory, both on-chip. The chip itself is manufactured by TSMC on a 65-nm fabrication process, and Lucid rates its power draw (presumably peak) at a relatively modest 6W.

Bringing the Hydra to market: Big Bang fizzles?
That's the hardware, pretty much, which is relatively straightforward. The story of the Hydra's current status is considerably more complex. Lucid says it has been working with a number of motherboard makers on products that will employ the Hydra chip. MSI has been furthest along in the process and, to our knowledge, is so far the only partner to reveal its plans to the public. Those plans center around a gamer-oriented motherboard based on the Intel P55 chipset dubbed the Big Bang Fuzion.

MSI's Big Bang Fuzion board

During IDF, MSI and Lucid announced plans for a public launch of the Big Bang motherboard on October 29. As we understand it, the idea was for the Big Bang board to be available to consumers for the holiday season, complete with a driver that supported both symmetrical—two or more identical video cards—and asymmetrical—a GeForce GTX 260, say, and a GeForce 9800 GTX—configurations. A new capability enabled by Windows 7, the ability to mix Radeons and GeForces in the same GPU team, would be enabled by a driver update at a future date.

However, October 29 came and went, and nothing happened—the Big Bang Fuzion wasn't launched. Rumors flew that the board had been delayed to the first quarter of next year. A certain someone pinned the blame on Nvidia, to the surprise of no one. The charges were plausible, though, because the Hydra's capabilities threaten Nvidia's SLI licensing regime, whereby motherboard makers must pay tribute to Nvidia in order to enable GeForce multi-GPU configurations on their products. It's conceivable Nvidia might have pressured MSI to delay the product.

According to a source familiar with the situation, MSI's requirements for the Hydra driver changed abruptly after the press blitz at this past IDF, with the schedule for support of mixed-vendor GPU configurations pulled into October, a dramatic acceleration of the original plans.

When asked for comment on this story, Nvidia spokesman Ken Brown told us that Nvidia welcomes new technology and innovation, especially those that improve gaming, and said he wasn't aware of Nvidia playing any role in the Big Bang Fuzion delay. Brown reiterated Nvidia's long-standing position that what Lucid is attempting to do is "very ambitious," "an enormous technological challenge," a position the firm has rather curiously communicated at every opportunity. Furthermore, though, he confirmed to us that Nvidia will not block its partners from producing motherboards that incorporate Lucid's technology.

For its part, MSI issued a statement here (at the bottom of the page) citing a two-fold reason for the delay related not to the Hydra hardware but the drivers: the need for better optimization and stability in Windows 7 and in multi-vendor GPU configs.

Everyone involved seems to agree that the Hydra 200 hardware is ready to go. Based on our brief hands-on experience with the Hydra in Lucid's offices, though, we think MSI's trepidation about the drivers may be warranted. Lucid gave us a preview of the mixed-vendor mode in action, and predictably, we ran into a minor glitch: the display appeared to be very dark, as if the gamma or brightness were set improperly, in DirectX 10 applications. This was a preview of that nascent functionality, though, so such things were expected at this stage.

More troubling was the obvious visual corruption we saw in DirectX 9 games when using an all-AMD mix of a Radeon HD 4980 and a Radeon HD 4770. The Lucid employees we spoke with about this problem attributed it to Windows 7, and indeed, Lucid VP of R&D and Engineering David Belz told us that Windows Vista had been the driver team's primary focus up until the last month. Belz said they had found few differences when moving to Windows 7, but forthrightly admitted the firm might need to look into those differences further. Belz seemed surprised when he asked what percentage of prospective Hydra buyers might wish to run Windows 7 immediately and we answered, "Uhh... 99%." The Hydra comes attached to a new motherboard, though, so one would think that answer would be rather obvious at this point in time, even if our estimate might be overstated by a few percentage points.

Belz did express confidence that the issues we saw were rather trivial, likely not difficult to fix with software tweaks. Given what we've seen of the Hydra in action, we're not inclined to disagree with that assessment.