The Commerce Department yesterday ruled that Japanese companies were selling some types of computer chips at prices below fair market value in the United States.

Joseph L. Parkinson -- chairman of Micron Technology Corp., the Idaho chip manufacturer that filed the complaint with the Commerce Department last June -- hailed the decision but said that "it does not restore" the thousands of U.S. jobs or the profits and research and development expenditures that have been lost because Japanese companies were dumping computer chips in the United States.

About $126 million of the chips in question -- 64K random access memory (RAM) components -- were imported from Japan last year, the Commerce Department said.

The International Trade Commission must decide within 45 days whether U.S. producers of these chips-used to store information for retrieval by computers-are being harmed or are likely to be by the Japanese producers.

If the commission, which is independent of the Commerce Department, finds that U.S. producers are being hurt, importers will have to pay a duty to offset the Japanese price advantage. The duties, called dumping margins, range from 11.87 percent on chips made by Hitachi Ltd. to 35.34 percent on chips sold by OKI Electric Industry Co.

Until the ITC decision, importers of 64K chips must post bonds or cash deposits equivalent to the dumping margins the Commerce Department established in its preliminary finding of dumping several months ago.

The U.S. semiconductor industry went into a nosedive last year -- in part, economists have said, because of worldwide overcapacity. Prices for 64K chips -- those that can store more than 64,000 pieces of information -- fell as much as 80 percent. The market has recovered slightly this year.

Charges also are pending against Japanese companies for dumping more sophisticated and bigger memory chips than the 64K chips that were the subject of yesterday's finding.

Although yesterday's ruling may further strain trade relations between the United States and its second-largest trading partner, the president of the Semiconductor Industry Association said the more important battles revolve about these more sohisticated computer chips.

Andrew A. Procassini, president of the trade association, said that the "real battleground" between U.S. producers and Japanese manufacturers is over 256K chips that can be programmed, erased and reprogrammed (called EPROMs), as well as 256K RAMs, which have about four times the storage capacity of the 64K chips.

The Commerce Department has reported preliminary findings that Japanese manufacturers are dumping both the 256K RAMs and the 256K EPROMs. The department must make a final determination by the end of July.

Parkinson said Micron Technology is a major manufacturer of the 256K RAMs, but disagreed with Procassini's assessment that the bigger and more sophisticated chips are more important. "The 64K market is the biggest market," he said.

If the ITC determines that the 64K chips are not damaging the U.S. semiconductor industry, no dumping duties will be assessed against the imports, and importers will get back any deposits they post.