Microsoft executives have urged hardware makers to build drivers for the upcoming 64-bit releases of Windows, lest the adoption of 64-bit computing be held back by hardware incompatibilities.

Microsoft will deliver versions of Windows XP and Windows Server 2003 for 64-bit Extended Systems in the fourth quarter.

Makers of hardware such as network interface cards, modems, graphics cards, printers and scanners have to develop 64-bit drivers for their products to work with the operating systems, Microsoft said.

"The app compatibility is good, the OS support is comprehensive. What's the one thing we need? 64-bit drivers. You guys have got to do the 64-bit drivers," Group Vice President Jim Allchin said.

The 64-bit platform processes more data per clock cycle, allows greater access to memory and speeds numeric calculations. Microsoft has worked with processor maker AMD to develop the 64-bit operating systems for its Athlon and Opteron chips. Athlon is meant for use in desktop computers, Opteron for server systems. 64-bit operating systems have been available on the competing Unix platform for years.

Microsoft expects significant adoption of 64-bit systems. By the end of 2005, all of the processors sold by AMD and the majority of processors sold by Intel will support 64-bit computing, Bill Gates has predicted. On the server, 64-bit will be common sense within the next couple of years and also on the desktop users will want to reap the benefits of the capabilities, he said. Intel earlier this year followed rival AMD in announcing a processor with 64-bit extensions technology.

Tim Wright, director of strategic marketing at AMD, agreed with Gates' prediction. "By the end of 2005, all we will be shipping is AMD 64," he said.

One key benefit of 64-bit extension technology and Microsoft's 64-bit operating systems is that applications written for 32-bit computers will still work with processors that can run 64-bit software. However, that is not true for device drivers, said Tom Phillips, general manager of Microsoft's hardware experience group. "Applications are generally running up in user land. In kernel land there is a far different development environment and we don't have the luxury of running software" that is actually not completely compatible with the hardware, he said.

Processor maker AMD is not worried about device driver trouble, although some peripherals initially may not work, said Wright. "There are a ton of device drivers that have already been written and the operating system has a bunch of built-in drivers," he said. Some of the companies that have already developed 64-bit drivers include Adaptec, Brother and Creative Labs, according to the AMD Web site.