Accessing SDRAM DIMM SPD eeprom

I'm going to give a try at accessing some DRAM DIMM eeprom (the one used for storing SPD data) via i2c. I wonder if somebody else did that too in the past and has some experience to share before I dig my hole too dip to get of it :slight_smile:

Mmhhh… I started the investigation with an old PC100 DIMM memory module. I’m getting strange results … I wonder if it’s me not testing it properly.

Anyway, I can detect the i2c address of the SPD eeprom, which is 83, and that’s a consistent result. I always get the same result using the very well know i2c_scanner of Tod E. Kurt.

But then, when I try and read every byte of it, I get inconsistent results, some portions of the memory footprint gets read ok, some other changes every time … I have to check for those wirings, maybe it’s just that.

Anyway, I can say it’s not that difficult to do. I wonder what will I read there inside :slight_smile:

I’m done. Everything went well at the end. Reading the PC100 SDRAM SPD eeprom with i2c and Arduino is easy if you wire it right (I did not at first!). I ended up wiring it directly to the eeprom ic with a few test hooks instead of using the board’s pinout.

Data can be interpreted using the following Intel doc: . It’s titled “PC SDRAM Serial Presence Detect (SPD) Specification” Rev.1.2A, December 1997, by Intel.

Just my 2cent to the community :slight_smile: