Intel quad-core microprocessors that work at an energy-efficient 50 watts per processor will officially be on the market starting today, according to the company.

Each of the four cores in its new Xeon L5320 and L5310 will consume just 12.5 watts of electricity, according to Intel. The company claims the new Xeons use between 35% and nearly 60% less power than its existing 80-watt and 120-watt quad-core server products.

The L5320 operates at 1.86 GHz and the L5310 at 1.60 GHz. They both feature 8M bytes of on-die cache for faster memory data communication. In quantities of 1,000 units, the L5320 is priced at $519 (£269) and the L5310 at $455 (£236).

The new Xeons can be coupled with Intel's existing Bensley server platform, replacing existing dual-core or quad-core Intel processors.

Intel and AMD are locked in competition for dominance in the quad-core chip market, as enterprises demand more performance out of servers. Meanwhile, customers are demanding greater energy efficiency as data centre power costs rise.

AMD in February released details of its coming new quad-core chip, code-named Barcelona, at a technical conference in San Francisco.

Barcelona, due to be released mid-year, improves performance and energy efficiency over the competition and over AMD's own dual-core processor, the Opteron, which it introduced in 2003, said Brent Kerby, product marketing manager for Opteron at the time.

Servers based on the new Xeons are expected to be available worldwide over the next few months from such server manufacturers as Dell, HP, IBM and others.