The bsp is the original bootloader from Linksys so if you want to run the
Linksys firmware on this router use the bsp.
If you want to run DD-WRT and not the Linksys firmware use the cfe.
If you are running DD-WRT you are using the cfe created for it.

-flash:bsp /noemw /noreset 
-backup:bsp /noemw /noreset 

If you backup the bsp it must be 320K in size if not you did it wrong
most likly use the wrong command -backup:cfe don't use that on a vxworks(BSP)
router running the Linksys firmware.
You must use -backup:bsp to get it off a vxworks unit.

BSP = VxWorks Bootloader
CFE = Linux Bootloader
The vxworks BSP is 320K bytes.(Board Support Package)
The linux CFE (Common Firmware Environment) is either 128K or 256K depending on manufacture and/or hardware.