ramdisk loading address in U-Boot

[HappyPhot]

Hi:
  I build a ramdisk image and mkimage for U-Boot
by using -a and -e = 4000000.
  In U-Boot command line, I type "tftpboot 2000000 ramdisk_image".
After bootm , the ramdisk is loaded to "0fdea000", like:

## initrd at 0x02000040 ... 0x02185BD0 (len=1596305=0x185B91)
   Loading Ramdisk to 0fdea000, end 0ff6fb91 ... OK
## Transferring control to Linux ....

  Why was the ramdisk loaded into 0fdea000, instead of 4000000 ?

thank you,
/HappyPhot