I tried using the MRC blob to compare the timings, but I must have done something wrong in my code as it didn't work at all
See following commits:
5c10abe nb/intel/sandybridge: increase MMCONF_BASE_ADDRESS
0306e6a intel/sandybridge: Fix builds with System Agent blob
f9c4197 northbridge/sandybridge/raminit_mrc.c: fix missing include
Was MRC blob ever really an option for lenovo/xxx boards? I did not check history.