AMD last week added to its Opteron 64bit processor line-up with the launch of the 800 series of multiprocessor chips and the 100 series for single-processor workstations and servers. The move increases the choice of processors for firms deploying 64bit systems for high-end applications, but AMD faces tough competition from the new Madison version of Intel's Itanium.

AMD Opteron processor models 840, 842 and 844, and models 140, 142 and 144 are available immediately. The two new ranges are aimed at eight-way and single-processor systems respectively. AMD's Opteron was introduced in April with the 200 series of dual-processor chips.

"AMD is now offering IT managers a complete range of 64bit solutions that are designed to protect investments in 32bit applications and lower their total cost of ownership," said Marty Seyer, vice president and general manager of AMD's microprocessor business unit.

Opteron chips are designed to run 32bit software such as Windows equally as well as new 64bit code. This capability has attracted some interest from enterprises, because it could let them make a gradual transition to 64bit systems without having to suddenly switch from 32bit applications in which they may have invested a lot. Intel's Itanium 64bit family, which was last week expanded with the addition of the Itanium 2 6M Madison chip, has a different architecture that only delivers optimum performance when running 64bit applications.

However, few enterprise vendors have so far announced plans to sell Opteron-based systems, while there is growing support for Intel's chips from firms such as HP and IBM. AMD does have cost on its side, however, with its top-end Opteron 844 chip priced at $2,149 (£1,300) while Intel's new Itanium 2 chip costs up to $4,226 (£2,540).

The model names of AMD's Opteron chips denote relative performance, so that a 144 is faster than a 142. The actual clock speeds vary between 1.4GHz and 1.8GHz. The 800 series chips for multiprocessor systems differ from the 100 series in their support for cache coherency in the high-speed HyperTransport communication links that connect them to other processors and the rest of the system.

This autumn, AMD is also set to ship a further 64bit chip, the Athlon 64, designed for mainstream desktops. This will have just a single HyperTransport link and a 64bit memory bus instead of the three HyperTransport links and 128bit bus of the Opterons, AMD said.

Volume prices for AMD's new Opterons are $749 (£450) for the 840, $1,299 (£780) for the 842, and $2,149 (£1,300) for the 844. The single-processor chips are priced at $229 (£140) for the 140, $438 (£260) for the 142, and $669 (£400) for the 144.