Write only memory

Write-only memory has been one of the best practical jokes on the electronics industry field.

Write-only memory (WOM) is the antithesis of read-only memory (ROM). By definition, a WOM is a memory device which can be written but never read. The WOM concept is most often used as a joke or a euphemism for a failed memory device.

An engineer at Signetics, frustrated by the long and useless sequence of approvals for data sheets (during which no actual checking occurred), once made up a spec for a “Write Only Memory” (a “WOM”) and sent it along with a batch of other data sheets to be approved. The WOM data sheet went through the approval chain, just fine, and wound up in Signetics’ new products catalog at 1970′s. Only after customers began asking for price and delivery. Signetics shortly printed up new “corrected” databooks, without any WOMs, and asked for the “erroneous” ones to be returned.

About 1974, Signetics bought a two-page, full-color spread in the April issue of ELECTRONICS Magazine, and published the WOM data sheet, as a (rather expensive) April Fool’s Joke. The data sheet is quite funny reading even today.



  1. Tomi Engdahl says:

    The Joker Behind the Signetics 25120 Write-Only Memory Chip Hoax

    engineers and hobbyists alike have enjoyed the classic 1972 April Fool’s joke by Signetics of the Signetics 25120 Write-Only Memory chip
    Now it seems that the previously anonymous practical joker has identified himself

    The Real Story of the Write-Only-Memory (WOM)

    I worked at Signetics as an engineer from about 1967 to 1979. One of my tasks in the Signetics MOS marketing group was to create data sheets for new products.

    I wrote the 25120 WOM data sheet, copyrighted in 1972, as a lark to see what a Signetics WOM specification might look like. I used a humorous EIMAC specification as a basis.

    I had always admired an EIMAC high powered vacuum tube spoof data sheet put out by Eitel-McCullough,Inc. I saw it when I was a teen Ham Operator and must have memorized it. That was in the late 1940’s.


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