IBM has quietly begun taking orders for its first ultra-thin "blade" server to be based on AMD's Opteron.

Called the AMD Opteron LS20, the server is based on IBM's BladeCenter design and will be available with a special low-power version of the Opteron.

The new server, which we were given a sneak peek of in March, will be the third Opteron product to be sold by IBM and begin shipping in June.

Blade servers, which slide into a common chassis much like books into a bookshelf, are much smaller and easier to configure than other types of servers. IBM executives had been promising to sell Operton-based blades since December, but the LS20 first appeared unannounced on the IBM's website on 3 May. News of its existence was first reported on The Register.

IBM was the only major server vendor to back AMD's 64-bit microprocessor when it was announced two years ago, but today IBM rivals HP and Sun offer a wider selection of Opteron-based systems.

The early support was a critical factor to Opteron's success, but now that other vendors have jumped on board, IBM may feel less pressure to expand its product line into markets that are not explicitly demanding Opteron, said Gordon Haff, an analyst with Illuminata.

"They will meet customer requirements, but they're certainly not going to proliferate Opteron models unnecessarily," Haff said. "The processors make sense for some types of applications, and blades are an attractive form factor, particularly if you're going to have a large number of servers."

The LS20 will be available with a special low-power 68-watt Opteron processor, which will make the server cooler than the typical Opteron system. Standard Opteron processors require 95 watts of power - about one-third more energy than the LS20.

AMD sells the 68-watt version of its 2.4GHz Opteron Model 250 to both HP and IBM, said an AMD spokesman. HP began shipping its first two Opteron-based blade servers, the ProLiant BL25p and BL35p, in March of this year.

IBM's servers will also ship with the 2.0GHz dual-core Model 270 processor, as well as two other single-core processors: the 2.0GHz Model 246 and the 2.6GHz Model 252.

The LS20 will support up to 8GB of DDR memory and as many as two U320 SCSI hard drives. It will be available with Windows or Red Hat or SuSE Linux.

Pricing starts at $2,259 for servers based on the 246 with 1GB of memory. An LS20 based on the 270 with the same amount of memory starts at $3,649.

More details on the new blades can be found here.