The Jargon File (version 4.4.7, 29 Dec 2003):

yoyo mode
 n.

    The state in which the system is said to be when it rapidly alternates
    several times between being up and being down. Interestingly (and perhaps
    not by coincidence), many hardware vendors give out free yoyos at Usenix
    exhibits.

    Sun Microsystems gave out logoized yoyos at SIGPLAN '88. Tourists staying
    at one of Atlanta's most respectable hotels were subsequently treated to
    the sight of 200 of the country's top computer scientists testing yo-yo
    algorithms in the lobby.


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

yoyo mode

    The state in which a computer is said to be when it
   rapidly alternates several times between being up and being
   down.  Interestingly (and perhaps not by coincidence), many
   hardware vendors give out free yoyos at Usenix exhibits.

   Sun Microsystems gave out logoised yoyos at SIGPLAN '88.
   Tourists staying at one of Atlanta's most respectable hotels
   were subsequently treated to the sight of 200 of the country's
   top computer scientists testing yo-yo algorithms in the
   lobby.

   [Is it "yoyo" or "yo-yo"?]

   [Jargon File]

   (1995-03-07)