[U-Boot] Using initramfs instead of an initrd image ?

[Chip]

Greetings,

Is there a way making uboot use initramfs images instead of initrd ?

I have a glacier AMCC460GT PPC board. I generate my initramfs image
from my rootfs directory as:

$ cd rootfs
$ find . | cpio -o -H newc | gzip > ../rootfs.img

so I tried first to use the initramfs image directly

=> tftp 1900000 glacier/rootfs.img
..
done
=> tftp 1000000 glacier/uImage
..
done
=> tftp 1800000 glacier/glacier.dtb
..
done

=> bootm 1000000 1900000 1800000
## Booting kernel from Legacy Image at 01000000 ...
   Image Name:   Linux-2.6.32
   Created:      2010-04-06  20:10:00 UTC
   Image Type:   PowerPC Linux Kernel Image (gzip compressed)
   Data Size:    1846014 Bytes =  1.8 MB
   Load Address: 00000000
   Entry Point:  00000000
   Verifying Checksum ... OK
Wrong Ramdisk Image Format
Ramdisk image is corrupt or invalid

OK so this doesn't work

then i tried packing the initramfs into a ramdisk image format

$ mkimage -A ppc -O linux -T ramdisk -a 0x1900000 -n "ramdisk" -d
rootfs.img rootfs2.img
Image Name:   ramdisk
Created:      Tue Apr  6 17:33:56 2010
Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
Data Size:    3332660 Bytes = 3254.55 kB = 3.18 MB
Load Address: 0x01900000
Entry Point:  0x01900000

=> tftp 19000000 glacier/rootfs2.img

still no luck

=> iminfo 1900000

## Checking Image at 01900000 ...
Unknown image format!

Thanks
Chip