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

write-only memory
 n.

    The obvious antonym to read-only memory. Out of frustration with the long
    and seemingly useless chain of approvals required of component
    specifications, during which no actual checking seemed to occur, an
    engineer at Signetics once created a specification for a write-only memory
    and included it with a bunch of other specifications to be approved. This
    inclusion came to the attention of Signetics management only when regular
    customers started calling and asking for pricing information. Signetics
    published a corrected edition of the data book and requested the return of
    the ?erroneous? ones. Later, in 1972, Signetics bought a double-page spread
    in Electronics magazine's April issue and used the spec as an April Fools'
    Day joke. Instead of the more conventional characteristic curves, the 25120
    ?fully encoded, 9046 x N, Random Access, write-only-memory? data sheet
    included diagrams of ?bit capacity vs.: Temp.?, ?Iff vs. Vff?, ?Number of
    pins remaining vs.: number of socket insertions?, and ?AQL vs.: selling
    price?. The 25120 required a 6.3 VAC VFF supply, a +10V VCC, and VDD of 0V,
    ?2%.


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

write-only memory
WOM

   1.  (WOM) The obvious antonym to "read-only
   memory" (ROM).

   Out of frustration with the long and seemingly useless chain
   of approvals required of component specifications, during
   which no actual checking seemed to occur, an engineer at
   Signetics once created a specification for a write-only
   memory and included it with a bunch of other specifications to
   be approved.  This inclusion came to the attention of
   Signetics management only when regular customers started
   calling and asking for pricing information.  Signetics
   published a corrected edition of the data book and requested
   the return of the "erroneous" ones.  Later, around 1974,
   Signetics bought a double-page spread in "Electronics"
   magazine's April issue and used the spec as an April Fools'
   Day joke.  Instead of the more conventional characteristic
   curves, the 25120 "fully encoded, 9046 x N, Random Access,
   write-only-memory" data sheet included diagrams of "bit
   capacity vs. Temp.", "Iff vs. Vff", "Number of pins remaining
   vs. number of socket insertions", and "AQL vs. selling price".
   The 25120 required a 6.3 VAC VFF supply, a +10V VCC, and VDD
   of 0V, +/- 2%.

   2. bit bucket.

   [Jargon File]

   (2007-03-24)