S/PDIF stands for Sony/Philips Digital Interface. In the photo above, the S/PDIF port is on the right side.
S/PDIF is an optical audio cable format that allows the transfer of digital audio signals from device to device without needing to convert to an analog signal first. This is beneficial since such a conversion can hurt audio quality.
S/PDIF ports are included on some motherboards, particularly a lot of high-end motherboards, although they are rarely used. You can also find them on certain laptops and desktops, sometimes in the same jack as the headphone jack.
This article is part of the Tom's Hardware Glossary.
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