A system and method for providing SDRAM mode register shadowing in a
memory system. A system includes a memory interface device adapted for
use in a memory system. The memory interface device includes an interface
to one or more ranks of memory devices, and each memory device includes
one or more types of mode registers. The memory interface device also
includes an interface to a memory bus for receiving commands from a
memory controller. The commands include a mode register set command
specifying a new mode register setting for one or more ranks of memory
devices and a mode register type. The memory interface device further
includes a mode register shadow module to capture settings applied to the
mode registers. The module includes a shadow register for each type of
mode register and a shadow log for each type of mode register. The module
also includes mode register shadow logic to detect a mode register set
command, to store the new mode register setting in the shadow register
corresponding to the specified mode register type, and to set one or more
bits in the shadow log corresponding to the specified mode register type
to indicate which of the ranks of memory devices have been programmed
with the new mode register setting.