Computer experts said yesterday that they had taken a big step toward making tiny, super-fast computers by creating a molecular "logic gate," which forms the basis of how a computer works.

Built on a crystalline structure, such computers, called molecular computers, will someday replace those based on silicon chips and could ultimately make it possible to have a computer so small it could be woven into clothing, they predicted.

They will need far less power than current computers and may be able to hold vast amounts of data permanently, doing away with the need to erase files.

"You can potentially do approximately 100 billion times better than a current Pentium [chip] in terms of energy required to do a calculation," University of California, Los Angeles chemistry professor James Heath said in a statement. Heath's team is at UCLA; the other team is based at Hewlett-Packard Co. in Palo Alto, Calif.

"We can potentially get the computational power of 100 workstations on the size of a grain of sand," he added.

"We have actually built the very simplest gates used in computers -- logic gates -- and they work," Phil Kuekes, a computer architect at Hewlett-Packard, said in a telephone interview.

Logic gates switch between on and off positions, creating the changes in electrical voltage that represent "bits" of information.

Heath's team did this by creating a new compound, called rotaxane, which grows in a crystalline structure. Heath and Kuekes' teams, in an article in the journal Science, wrote that the rotaxane molecules, sandwiched between metal electrodes, functioned as logic gates.

Computers are now based on silicon chips. The information they carry is etched onto them, and it is becoming increasingly harder to do this precisely on ever-smaller chips.

But a crystal can absorb information, in the form of an electrical charge, and organize it more efficiently.

The next step will be structuring the chip. Instead of etching this structure onto the surface, as is done now with silicon chips, it will be downloaded electrically.