The Free On-line Dictionary of Computing (30 December 2018):

Industry Standard Architecture
AT bus architecture
ISA bus

    (ISA) A bus standard for IBM
   compatibles that extends the XT bus architecture to 16
   bits.  It also allows for bus mastering although only the
   first 16 MB of main memory is available for direct access.
   In reference to the XT bus architecture it is sometimes
   referred to as "AT bus architecture".

   Compare EISA, MCA.

   (1996-06-25)