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Quoting from the Wikipedia article, Rollover (key):

Modern keyboards detect ghosting and instead of registering a fourth key will ignore the third key, which is known as blocking.

Are there utilities that run on a PC and that allow me to check if the keyboard is using blocking to prevent ghosting? (I am using a ThinkPad keyboard.)

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Key blocking can be seen quite easily in Windows XP, and possibly even without OS. Example, using the German keyboard on a Thinkpad T41:

  1. Hold E

  2. Hold R

    Result: r is repeatedly printed on screen.

  3. Hold T

    Result: Windows will stop repeating r; instead, it will beep. Likely explanation: Otherwise the keyboard controller can not distinguish between E and R (ghosting).

  4. Release T

  5. Hold W

    Result: This time, the character is displayed without problem, showing a w repeating on screen.

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