IBM is set to announce it will expand its line of servers powered by chips from AMD, its latest attempt to compete with Sun and HP.

IBM already sells low-end servers with AMD's Opteron chips, so the move will allow the company to offer more choice in its high-end, commercial line.

The company would not confirm the details, but said its systems division, responsible for designing servers and chips, would announce new products and partnerships in "our biggest announcement of the year," according to IBM spokeswoman Joanna Brewer.

Sun, a competitor in the server market, said the change would not help IBM win new market share, since Sun's Solaris operating system still holds an advantage in security and open-source development compared to IBM's AIX.

"Sun has a two-year head start and an even longer real-world advantage over Big Blue's x64 Opteron. Big Blue can't match-up, let alone catch-up, to Sun's awesome AMD-based systems," said Larry Singer, Sun's senior vice president and strategic insights officer.

Sun will compete with any future IBM products with the three servers it launched 11 July: Sun Fire x4600, 8000 and x4500.

IBM's move would be welcome news for AMD, which has watched rival Intel seize the spotlight in recent weeks by announcing a handful of new chips, including the Montecito Itanium 2 and the Woodcrest Xeon 5100 for servers, the Conroe Core 2 Duo for desktops and the Merom Core 2 Duo for notebooks.

AMD is set to hit back at Intel with a 15 August launch of a new design called "Rev. F." The Opteron upgrade may be one reason that IBM would decide to expand its AMD-based server line, said Gordon Haff, an analyst with Illuminata.

"It's ironic because IBM was a critical early partner for AMD; they were the tier-one vendor up on stage at the Opteron launch. But since then, they have done relatively little compared to HP and Sun," he said.