Serial Presence Detect

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What Does Serial Presence Detect Mean?

Serial presence detect (SPD) is information stored on an EEPROM chip when a computer is booted. It is located on an SDRAM memory module and communicates to the BIOS the module size, data width, speed and voltage, which are used to configure the module memory controller for maximum reliability and performance.

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Techopedia Explains Serial Presence Detect

The manufacturer of the memory module will put the SPD information on the EEPROM chip. When a computer is turned on, if the BIOS is not provided with SPD, it will assume the memory module information, which presents no problem to some memory modules.

Parallel presence detect (PPD) data was used in earlier 72-pin SIMMs. However, the standard changed to SPD with the later model 168-pin DIMM. SPD encodes much more information.

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Margaret Rouse
Technology Expert
Margaret Rouse
Technology Expert

Margaret is an award-winning technical writer and teacher known for her ability to explain complex technical subjects to a non-technical business audience. Over the past twenty years, her IT definitions have been published by Que in an encyclopedia of technology terms and cited in articles by the New York Times, Time Magazine, USA Today, ZDNet, PC Magazine, and Discovery Magazine. She joined Techopedia in 2011. Margaret's idea of a fun day is helping IT and business professionals learn to speak each other’s highly specialized languages.