Science: Crystal Memory

The most important part of a brain, human or electronic, is its memory—a place where information can be stored until it is needed. Electronic memories cannot approach human ones. Their capacity is small, and the storage places (electron tubes, magnetic drums and the like) are bulky. Some of them can remember only for fractions of a second. If the memories are stored on punchcards or magnetic tapes, the machine cannot bring them to mind without slow mechanical pondering.

In the current Electrical Engineering, J. R. Anderson of Bell Telephone Laboratories tells about a new electronic device which may solve the memory problem. Its new feature is a thin slice of crystalline barium titanate. This peculiar stuff is “ferroelectric”: i.e., if it is placed between two metal contacts, a considerable amount of electrical energy can be made to flow into the crystal and stay there. There is room for 2,500 dots of energy on a one-inch square of crystal.

Each one of these dots can hold what computer men call a “bit” (short for binary digit) of information. If charged, it is considered a “one”; if uncharged, it is a “zero.” By arranging ones and zeros in a code, a string of numbers, letters or words can be stored in dot form (2,500 bits is the equivalent of 69 words). When the crystal has heard its lesson once, it remembers for a week or more.

The bits can be “read out” by sending pulses of electricity to the dots on the crystal. Each dot absorbs more or less electricity according to whether it is charged or not. Sensitive relays measure the flow of current and report whether each dot is a one or a zero. This process, which takes less than a millionth of a second, is the equivalent of the human brain’s “bringing something to mind.”

Anderson’s memory crystals are still only partly developed, but he has high hopes for them. They occupy little space and demand little current. They are thus worthy teammates for the tiny germanium transistors (TIME, Feb. 11) which will be the brain cells of the supercomputers of the future.