Hi Mart,
you wrote that RAM check fails during initram for the Geode LX. AFAICS that is expected due to MSR_GLIU0_SYSMEM not being set at that stage, so any accesses to stuff above 1M will end up nowhere. northbridge_init_early() provided a clue about this behaviour. I hope this observation will help you work around the RAM check breakage.
Regards, Carl-Daniel