C2600 platform with 65536 Kbytes of main memory and 16 MB extra flash memory. I had no memory in the “System-code SIMM (Flash memory)” slot, since the 2651XM must ship with 16 MB on the motherboard. Once I snapped in the extra memory, my router recognized it without any trouble. IOS was 12.2(11)T10, which corresponded to the c2600-ik9s-mz.122-11.T10.bin image. The’show flash’ command showed this after the memory upgrades:”]
Source: https://taosecurity.blogspot.com/2004/05/upgrading-cisco-router-ios-today-i.html