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

Xerox Data Systems Model 940
SDS 940
XDS 940

    (SDS 940, XDS 940) A time-sharing system,
   announced in February 1966, developed by Scientific Data
   Systems with help from The University of California at
   Berkeley and Tymshare.  SDS 940 was backward compatible
   with SDS's previous systems (except the 12-bit SDS 92).  It
   had monitor and user modes, dynamic program relocation,
   automatic memory fragmentation, and system protection.

   After 1968 Xerox bought out SDS and renamed the SDS machines
   "Xerox Data Systems" (XDS).  Xerox then produced the XDS
   530.

   (2004-06-17)