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

Slot 1

    The physical and electrical specification
   for the connector used by some of Intel's microprocessor
   cards, currently (August 1999) the SEPP Celeron and the
   SECC Pentium II.

   Slot 1 is a departure from the square ZIF PGA/SPGA
   sockets used by Pentium and earlier processors, the
   processor being mounted on a card, with a 242-lead
   edge-connector.

   The Slot 1 specification allows for higher bus rates than
   Socket 7.  Slot 1 motherboards use the GTL+ bus
   protocol.

   See also Slot 2, Slot A.

   [bus rates?]

   (1999-08-04)