AMD's upcoming M780 laptop chipset - designed to be paired with the company's next-gen mobile processor, 'Griffin' - will allow the system to flip between integrated and discrete graphics engines on the fly, the chip maker has revealed.

The M780 is a mobile version of the RS780 desktop chipset, details of which leaked out onto the web a couple of months back. AMD today published some key M780 specifications which largely confirm what we already knew about the desktop version, due to go on sale as the 780G.

Both chipsets incorporate an R600-derived DirectX 10-compatible graphics core and support PCI Express 2 for the addition of discrete GPU chips and other add-ins.

AMD didn't provide any further details about the on-board GPU, but it did confirm the core contains its Universal Video Decoder (UVD) engine and can feed native links to DVI, HDMI, TV, CRT and LVDS display systems through two independent display controllers. Interestingly, the M780 will also support DisplayPort, the VESA-backed alternative to HDMI.

The M780's most interesting feature is PowerXPress - no relation to QuarkXPress - that allows laptops with two GPUs - one discrete, the other integrated into the chipset - to flip dynamically between the two without the need to restart the computer.

PowerXPress is controlled through a unified driver, so it's likely that the technology will only be offered on laptops with AMD's own chipset and standalone GPUs on board.

AMD is pitching the technology as a power-saving feature - it envisages the system automatically switching to the discrete chip when the laptop's plugged into the mains, then over to the integrated GPU when it's running on battery. Company representatives couldn't or wouldn't say whether this policy can be altered by the user, or will be exposed only to notebook manufacturers.

Still, if it's done through the driver, some enterprising coder will quickly publish a utility to allow users to switch GPUs at will.

Nvidia is known to be working on a similar technology, to be embedded in its own mobile chipsets and GPUs, though it's not yet clear when this will come to market.

The M780 will also incorporate Windows Vista-boosting Flash cache technology.

Since Griffin is a HyperTransport 3 chip, so too is the M780, and the chipset is compatible with Griffin's new power management techniques. As per the desktop 780G, the M780 connects to AMD's SB700 Southbridge chip, which is now confirmed to provide 14 USB ports, PCI connectivity, links to parallel ATA devices and six SATA ports.

The M780 is due to debut in H1 2008. Together with Griffin it will form AMD's 'Puma' laptop platform, though like today's 'Kite' platform, it won't be marketed the way Intel markets Centrino, AMD officials said.