An isolinear subprocessor or isolinear data subprocessor was a computer core subsection containing isolinear optical chips.
In 2367, Worf and Riker were working inside of a Jefferies tube on an isolinear subprocessor that included panel J-14 Baker. This panel connected to Science Station Two, and functioned as part of the USS Enterprise-D's life support system. (TNG: "Brothers")
In 2370, when Doctor Julian Bashir expressed surprise that Elim Garak could fix computers, Garak replied that he dabbled with isolinear data subprocessors as a hobby. (DS9: "Cardassians")