Cisco GSR12/60 - 12012 Router -AnyLAN, SONET/SDH Installation And Configuration Manual page 46

Physical and Functional Overviews
Note
SDRAM
SDRAM stores routing tables, protocols, and network accounting applications, and runs the
Cisco IOS software. The default PRP configuration includes 512 MB of error checking and
correction (ECC) SDRAM. DIMM upgrades of 512 MB and 1 GB are available. You
cannot mix memory sizes. If two DIMMS are installed, they must be the same memory size.
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If a single DIMM module is installed, it must be placed in bank 1 (U15).