decode-dimms is a small utility that displays the contents of DIMM memory SPD ROMs in human-readable form. (It is part of a larger collection of https://git.kernel.org/pub/scm/utils/i2c-tools - most of which is very Linux-specific.) This version of decode-dimms can even directly read the SPD ROM data from the sysctl variables created by NetBSD's spdmem(4) device driver.