With Nvidia engaged in damage control after receiving numerous complaints from disgruntled gamers about the performance of its graphics processors on Windows Vista, archrival ATI hopes to capitalise on the situation.

ATI, a subsidiary of AMD that is the second-largest maker of standalone graphics card chips, claims that its Catalyst line of drivers is enabling almost all of its game-playing customers to use Vista problem-free or with miniscule drops in performance from what they were getting on Windows XP.

"We're seeing less than a 5 percent gap on average," Ben BarHaim, said vice president of ATI's software engineering division. He added that ATI has been working "very closely" with Microsoft on Vista over the past four years and that all of the company's drivers are now certified by Microsoft's Windows Hardware Quality Labs (WHQL) operation.

Even before Vista's general release on 30 January, gamers using beta versions of the new operating system had reported problems in importing games written for Windows XP and its DirectX 9 graphics engine. The problems primarily involved slow animation performance in graphically-intense, first-person shooter games such as CounterStrike, Half-Life 2, Doom 3 and F.E.A.R., as well as occasional system crashes.

Vista is backward compatible with DirectX 9, for which virtually all PC games available today were written. It also introduces a new graphics engine, called DirectX 10, that eventually should allow games to run faster and display more textured, lifelike images than DirectX 9 supports, according to Microsoft. But a mere handful of games have been written specifically for Vista and DirectX 10 thus far.

Nvidia has beaten ATI to market with the first processor that is compatible with DirectX 10, its GeForce 8800 chip. But Nvidia also appears to have received more complaints than ATI has about malfunctioning drivers for its older processors.

Some unhappy users have even set up a website threatening Nvidia with a class-action lawsuit over its Vista drivers, some of which remain in beta form and lack Microsoft's WHQL certification.

Daniel Vivoli, senior vice president of marketing at Nvidia, acknowledged earlier this month that the company missed some issues during its quality assurance testing, and said that it is devoting heavy resources to fixing the Vista drivers. In addition, Nvidia has created a page on its website where Vista users can report bugs that they've found in its drivers.

ATI isn't immune to complaints about its drivers from gamers. But BarHaim claimed that it has received fewer complaints than Nvidia because all of its drivers – enabling video cards released as long ago as mid-2002 to work with Vista – have been fully tested and WHQL-certified.

Indeed, ATI hopes ongoing improvements to the Catalyst drivers eventually will allow games written for Windows XP to run as fast - or even faster - on Vista. "There is nothing that says we couldn't optimise a driver to run faster in Vista than XP," BarHaim said.

According to Jon Peddie Research, a market research and consulting firm, ATI ranked third overall in the PC graphics market in last year's fourth quarter, with a 23 percent market share. Nvidia was second with 29 percent of the market, and Intel led the way with a 37 percent share. But all of Intel's graphics chips are integrated directly with its mainstream processors, and gamers generally don't consider them to be high-performance devices.

AMD, which acquired ATI last October, has said that it plans to start selling integrated chipsets combining its x86 processors with ATI's graphics chips by 2009.

In the meantime, ATI is trying to win back customer mindshare in the high-end segment of the graphics card market, for devices costing $300 or more. That segment tends to generate the highest profits for ATI and Nvidia, and it also can lead to trickle-down success or failure for their midrange and low-end offerings. ATI holds about 40 percent of the high-end market, while Nvidia controls 60 percent, according to figures from market tracker Mercury Research that were provided by ATI.

ATI also confirmed that it's nearing the release of its first processor optimised for the DirectX 10 graphics engine in Vista. Pictures of ATI's Radeon R600, which would match up against Nvidia's GeForce 8800, began circulating on the web earlier this month. "You can assume that something – more news, or a release – will be coming in the next month or two," an ATI spokeswoman said.