From
Star Trek:
Sophisticated information storage and processing devices used by Starfleet after 2329 replacing duotronics. Isolinear chips were in general use in 2349. They are composed of linear memory crystal material.
For large computer systems isolinear chips are usually placed in wall-mounted racks. Allowing simultaneously computer access to hundreds of them.
Isolinear chips are simulair to isolinear rods used by the Cardassians.