Hi Vladimir,
since you have REed the raminit for Nehalem I'd like you to ask if you have any knowledge, information or pointers about using 8 GB DIMMs with it or even using more than 8 GB in total. In my case it is about an Arrandale i5-520M (in a Thinkpad 410s).
I know that an i7-820QM (Clarksfield) is perfectly capable of working with 8 GB DIMMs and probably up to 32 GB or even more (the Thinkpad W510 has 4 DIMM slots and I have tested it with 20 GB) and that is from around the same time as the Arrendale chips - which does not mean anything but I still refuse to accept that Nehalem is that limited. The official specs are not trustworthy IMHO and cpuid(1) and /proc/cpuinfo show the same physical address width of 36 bits (which would indicate a maximum of 64 GB).
The current raminit for Nehalem in coreboot is not able to train the two 8 GB DIMMs I have tested so far. I have added a debug output to choose_reg178 in the first loop before the margins are compared to STANDARD_MIN_MARGIN that shows that all margins are 0. If there is anything I could try or information I can provide, please let me know.
The (ancient) vendor firmware I've been using on the T410s does sometimes manage to boot Linux with an 8 GB DIMM (dmesg is attached including the e820 map), but it is quite broken and memtest86 locks up or reboots within seconds so that's probably not a good target for RE efforts. :)