SPD Data

Had a late night here in work last night and tried to get to grips with SPD Data. When I say SPD data, specifically I'm talking about the SPD data for DDR3 DIMM's. What's SPD data you say? It's a table of the timings and settings saved in an EEPROM on the DIMM (Dual Inline Memory Module) module itself. SPD (Serial Presence Detect) is usually a small EEPROM (Electrically Erasable Programmable Read-Only Memory) usually an Atmel 24C02. This is a 2Kb part 8 pin SOIC (Small Order Integrated Circuit) which is enough to store all the settings for your DIMM module.

Using the SPD Tool I mentioned in my last blog entry, you can customise the exact timings on your DIMM, unfortunately though at the moment, it only supports DDR2 and below. The other way to do it is through your BIOS.


Here's a great website which explains each byte in little detail. You can work it out from there. It covers DDR3, DDR2 and the older DDR.

Understanding DDR3 Serial Presence Detect (SPD) Table

DDR2 DIMM SPD Definition

There's also a few interesting publications in there about how DDR3 memory works and an informative one on how to reball and recover DDR2 memory chips. Obviously the tools used in reballing are only used in manufacturing plants, but it's still interesting to see.

How DDR3 Memory Works ?
How to Reball and Recover DDR2 Memory Chips