Nvidia on-the-fly GPU switching desktop debut due Q1 '08

Nvidia will bring the ability to flip at will between integrated and discrete graphics cores to the desktop early next year, courtesy of upcoming AMD-oriented chipset the MCP78S.

The chipset incorporates a GeForce 8-class DirectX 10, Shader Model 4.0 graphics engine, but it's also capable of driving a PCI Express 2.0 graphics card connected via the chipset's 16 PCIe 2.0 lanes, a presentation slide posted by Hexus.net reveals.

That's broadly what most integrated chipsets do, but the MCP78S also supports Hybrid SLI, which allows the user to flip between the two GPUs according to need. Need 3D performance for gaming? Activate the graphics card. The rest of the time: host the system's graphics on the lower-power integrated GPU.

Switching between the two can take place on the fly, unlike past attempts to do this, all of which required a restart. That was enough to put most users off utilitising the option.

Hybrid SLI first emerged back in July 2006 under the name 'SLI Power'. Since then, AMD began talking up PowerXPress, its name for the notebook-oriented version of the technique that's set to debut in AMD's 'M780' mobile chipset in Q1 2008.

Nvidia renamed SLI Power as Hybrid SLI back in June this year but then was pitching the technology as a notebook feature. Laptops are, after all, more sensitive to power draw than desktops. However, it's clear from the latest reports that Nvidia reckons it'll be useful for desktops too.

Current concerns about performance-per-Watt have already driven AMD to incorporate power-saving technology in its new ATI Radeon HD 3800 series of GPUs, all of which clock down according to the kind of apps the user is running, the better to minimise desktop power draw.

In addition to Hybrid SLI, the MCP78S will support Socket AM2 and AM2+ CPUs over a 2600MT/s HyperTransport 3.0 bus. It will also handle six 3Gb/s SATA drives, 12 USB ports and Gigabit Ethernet.

Separately, early 2008 will also see the arrival of Nvidia nForce 780-based motherboards, a month after the chip makers launches the chipset, it has been claimed.

The 780 will appear as the 780i SLI - aka 'C72XE' - and the 780a SLI - 'C72P' - targeting Intel and AMD platforms, respectively. Both chipsets will drive three PCI Express 2.0 x16 graphics card slots for 'tri-SLI' operation, mobo-maker moles claim.

Both are high-end chipsets aimed at gamers who might otherwise opt for Intel's X38 or the upcoming X48.