nVidia uses the IGP along with the discrete card, not just 1 of the 2, hence the name Hybrid SLi.
UPDATE: Adding slides from a presentation by Nvidia Corp.
There is always a trade-off between power consumption and performance in the world of 3D graphics cards. If one solution delivers high framerate per second, it most probably consumes significant amount of power, whereas another, which power consumption is minimal, cannot offer really high performance. But Nvidia recently announced that its new technology will meet low power consumption with high performance.
Nvidia’s new Hybrid SLI technology will have two modes and that will target different applications: the Power Saving Mode, which will switch off discrete graphics core and use only integrated graphics engine when high performance is not needed, whereas Max Performance Mode will make integrated graphics processor (IGP) to assist discrete graphics processing unit (GPU) and boost performance when it is required.
Even though Nvidia’s multi-GPU SLI technology enables significant performance increases, it also boosts power consumption, which means additional heat and higher noise levels. In this case, hybrid SLI’s power saving mode will allow to disable two high-performance graphics boards, such as Nvidia GeForce 8800-series when their 3D graphics firepower is not needed, Nvidia explained. The same mode will allow to integrate higher-performance graphics cores into notebooks without sacrificing battery life, as in case of battery operation only IGP will be used.
The max performance mode of hybrid SLI will allow systems featuring entry-level or mainstream GPUs from Nvidia to process graphics faster, as IGP will be able to help discrete graphics chip to render complex graphics, according to the company.
“[With] Hybrid SLI you have a discrete and a motherboard GPU in a system. When you switch between GPUs, you don’t have to unplug and plug monitor… What we have [implemented] on the core-logic site is [ability] to render in all cases through motherboard GPU,” explained Jeff Fisher, Nvidia’s general manager of GPU business unit, at a meeting with analysts.
Jen Hsun Huang, chief executive of Nvidia Corp. said that the first systems featuring hybrid SLI technology will be available late this year. No other details were disclosed.