NEW YORK (AP) _ Japan's leading corporate research laboratory on Wednesday announced the creation of a test model of a computer memory chip that is two generations ahead of the most powerful ones in use today.

However, researchers for Nippon Telegraph & Telephone Corp. - sometimes described as Japan's equivalent of AT&T Bell Laboratories - told fellow scientists in response to questions that the chip was created to test certain innovations and is not ready for production.

NTT stirred up the scientific community earlier this year when word circulated that it had created one of the chips, known as a 16-megabit dynamic random access memory (D-RAM). No other company has built a test model of a memory chip with that much capacity.

The paper was presented at the International Solid State Circuits Conference in New York, an annual forum for discussion of the state of the art in the integrated circuits used in electronic products ranging from computers to missiles.

Of more commercial significance are 4-megabit memory chips, which could begin appearing in computers within one or two years. Papers on chips of that size were presented by International Business Machines Corp. and Japan's Hitachi Ltd. and Mitsubishi Electric Corp.

IBM's 4-megabit chip has been produced on a regular production line in Essex Junction, Vt., and is past the prototype stage, the company says.

A 4-megabit chip is one that can store about 4 million bits of information, or roughly 400 pages of double-spaced, typewritten text. IBM's prototype can retrieve any bit of information in 65 billionths of a second, which is faster than its latest 1-megabit chip in spite of the higher density, the company said.

IBM said the production of its chip on its regular 1-megabit chip line ''demonstrates the chip's manufacturability and its potential for volume production.''

NTT said its 16-megabit chip - capable of containing more than 16 million bits of information - was manufactured using a technique that does not lend itself to manufacturing. Half of the 20 layers of the chip were etched using an electron beam instead of the normal method of shining light through a stencil.

NTT does not make its own chips but licenses its technologies to chip makers such as Hitachi, NEC and Mitsubishi.