|Hands on with Lucid's Hydra GPU load balancer|
|Written by TechReport|
|Thursday, 12 November 2009|
Hands on with Lucid's Hydra GPU load balancer
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. TechReport