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
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
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: http://www.taricorp.net/wp-content/uploads/2012/04/SPDSDRAM1.2a1.pdf . It’s titled “PC SDRAM Serial Presence Detect (SPD) Specification” Rev.1.2A, December 1997, by Intel.
Just my 2cent to the community