PCI express cards have an edge connector with a little notch in it to prevent the card from moving if the socket is longer than the connector. Additionally, the printed circuit board has a protrusion in front of the actual connector. What is its purpose?

Depicted below is a PCIe card. You can clearly see the protrusion I mean to the left of the edge connector. PCIe card

Picture from Wikimedia Commons by Clemens PFEIFFER, Vienna.

  • \$\begingroup\$ @JCRM Indeed! Sorry for this weird typo. \$\endgroup\$
    – FUZxxl
    Jan 30, 2018 at 15:44

1 Answer 1


According to the PCI Express Card Electromechanical Specification 1.1 it is to prevent insertion into a standard "non-express" PCI socket.

Excerpt from linked document

http://read.pudn.com/downloads166/ebook/758109/PCI_Express_CEM_1.1.pdf [page 72]


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