F3 initrd strangeness

[T. Horsnell (tsh)]

I'm having problems building a diskless net-bootable FC3 kernel,
and decided to take a look inside the vanilla initrd file
initrd-2.6.9-1.667.img. However, if I gunzip this and try
to mount it, the mount fails:

[root at fw1 ~]$ gunzip -c initrd-2.6.9-1.667.img > initrd-2.6.9-1.667
[root at fw1 ~]$ ls -l initrd-2.6.9-1.667*
-rw-r--r--  1 root root 1215488 Dec  6 15:29 initrd-2.6.9-1.667
-rw-r--r--  1 root root  530308 Dec  6 15:29 initrd-2.6.9-1.667.img
[root at fw1 ~]$ mount -o loop -t ext2 /root/initrd-2.6.9-1.667 /mnt
mount: wrong fs type, bad option, bad superblock on /dev/loop0,
       or too many mounted file systems
       (could this be the IDE device where you in fact use
       ide-scsi so that sr0 or sda or so is needed?)


If I do the same with a copy of the initrd from the vanilla
FC2 distribution all is well:

[root at fw1 ~]$ gunzip -c initrd-2.6.5-1.358.img > initrd-2.6.5-1.358
[root at fw1 ~]$ ls -l initrd-2.6.5-1.358*
-rw-r--r--  1 root root 8192000 Dec  6 15:22 initrd-2.6.5-1.358
-rw-r--r--  1 root root  267159 Dec  6 15:28 initrd-2.6.5-1.358.img
[root at fw1 ~]$ mount -o loop -t ext2 /root/initrd-2.6.5-1.358 /mnt
[root at fw1 ~]$ ls -l /mnt
total 9
drwxr-xr-x  2 root root 1024 Oct 19 21:38 bin
drwxr-xr-x  2 root root 1024 Oct 19 21:38 dev
drwxr-xr-x  2 root root 1024 Oct 19 21:38 etc
drwxr-xr-x  2 root root 1024 Oct 19 21:38 lib
-rwxr-xr-x  1 root root  733 Oct 19 21:38 linuxrc
drwxr-xr-x  2 root root 1024 Oct 19 21:38 loopfs
drwxr-xr-x  2 root root 1024 Oct 19 21:38 proc
lrwxrwxrwx  1 root root    3 Oct 19 21:38 sbin -> bin
drwxr-xr-x  2 root root 1024 Oct 19 21:38 sys
drwxr-xr-x  2 root root 1024 Oct 19 21:38 sysroot

I've tried several variations of  -o blocksize= without
success. I'm curious why the gunzip'd FC3 initrd is so much
smaller than the FC2 one, and yet the gzip'd .img is
much bigger.

Can anyone else successfully mount their FC3 initrd?
Any ideas what may be stopping me?

Cheers,
Terry.