Various methods of getting information about what's in the box and what's connected to the box.
Reads what's reported by the SMBIOS (System Management BIOS), for example memory controllers, etc. Memory controllers give information on how much memory can be installed, and the maximum module size.
lm-sensors is a hardware-probing tool. Provides module eeprom, which is used in reading memory module SPD (Serial Presence Detect).
i2c tools pretty-prints the output of something in lm-sensors for humans with the decode-dimms script. Pretty useful stuff!
… has a bunch of ls* utilities, like lshw.