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IT Support & Hardware · Advanced

Serial Presence Detect (SPD)

A small EEPROM on a memory module that stores its size, speed, timings, and voltage.

Definition

Firmware reads SPD at boot to configure memory correctly, and XMP/EXPO profiles are stored here too. Diagnostic tools read SPD to identify installed modules without opening the case. Corrupted SPD data can cause a module to be misdetected.

Example

CPU-Z's SPD tab shows each module's part number and supported profiles.

Exam tip

SPD is how the BIOS knows what RAM is installed; it is not where data is stored.

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