My purchased 128mb flash just arrived in my mailbox. Well it was empty, nothing inside…so Cisco router will boot into rommon.
Here are the parameters that are REQUIRED:
IP_ADDRESS
IP_SUBNET_MASK
TFTP_SERVER
TFTP_FILE
DEFAULT_GATEWAY
WARNING: Once you finished transferring file to the flash using tftp all your previously stored contents within the flash will be wiped out!
tftpdnld -u Means upgrade flash with software, after download is completed router will reboot automatically.
tftpdnld -r Means do not write to flash, write to ram.
tftpdnld without any option, the copied ios after checksum is validated will transfer the entire ios into the flash, and flash will be formatted automatically.
I was using 3com tftp server which is really really old, most tftp implementation has a maximum transfer size of 32MB, my rommon transfer failed with IOS that is more than 32MB.
cyruslab 
Thanks..
My Cisco 2610XM was crashed due to an IOS upgrade, which required more dram. I will try this now