yum and multiple architectures... more pain!

[Andrea]

More nightmares trying to remove a devel package from Fedora 8 on PS3.
I'd like to replace alsa-lib-devel.ppc64 with alsa-lib-devel.ppc.

Why does yum want to remove all those ppc devel packages when I ask to remove a ppc64 devel?

[root at ps3 ~]# yum erase alsa-lib-devel.ppc64
.....

Dependencies Resolved

=============================================================================
  Package                 Arch       Version          Repository        Size
=============================================================================
Removing:
  alsa-lib-devel          ppc64      1.0.15-1.fc8     installed         8.2 M
Removing for dependencies:
  SDL-devel               ppc        1.2.13-2.fc8     installed         1.4 M
  SDL-devel               ppc64      1.2.13-2.fc8     installed         1.4 M
  eel2-devel              ppc64      2.20.0-1.fc8     installed         214 k
  eel2-devel              ppc        2.20.0-1.fc8     installed         214 k
  esound-devel            ppc64      1:0.2.38-6.fc8   installed          22 k
  evolution-data-server-devel  ppc64      1.12.3-2.fc8     installed         5.9 M
  evolution-data-server-devel  ppc        1.12.3-2.fc8     installed         5.9 M
  gnome-desktop-devel     ppc        2.20.3-1.fc8     installed         191 k
  gnome-desktop-devel     ppc64      2.20.3-1.fc8     installed         191 k
  gnome-panel-devel       ppc64      2.20.3-1.fc8     installed         177 k
  gnome-panel-devel       ppc        2.20.3-1.fc8     installed         177 k
  gnome-pilot-devel       ppc64      2.0.15-10.fc8    installed         164 k
  gnome-pilot-devel       ppc        2.0.15-10.fc8    installed         164 k
  libbonoboui-devel       ppc64      2.20.0-1.fc8     installed         1.0 M
  libbonoboui-devel       ppc        2.20.0-1.fc8     installed         1.0 M
  libcroco-devel          ppc64      0.6.1-3.fc8      installed         110 k
  libgnome-devel          ppc        2.20.1-2.fc8     installed         537 k
  libgnome-devel          ppc64      2.20.1-2.fc8     installed         537 k
  libgnomeui-devel        ppc        2.20.1.1-1.fc8   installed         2.4 M
  libgnomeui-devel        ppc64      2.20.1.1-1.fc8   installed         2.4 M
  librsvg2-devel          ppc64      2.18.2-2.fc8     installed          92 k




Even more strange when I try to reinstall SDL-devel.ppc (which had been removed as depending on 
alsa-lib-devel.ppc64) I get

[root at ps3 ~]# yum install SDL-devel.ppc
Setting up Install Process
Parsing package install arguments
Resolving Dependencies
--> Running transaction check
---> Package SDL-devel.ppc 0:1.2.13-2.fc8 set to be updated
--> Processing Dependency: alsa-lib-devel for package: SDL-devel
--> Running transaction check
---> Package alsa-lib-devel.ppc 0:1.0.15-1.fc8 set to be updated
--> Finished Dependency Resolution

Dependencies Resolved

=============================================================================
  Package                 Arch       Version          Repository        Size
=============================================================================
Installing:
  SDL-devel               ppc        1.2.13-2.fc8     updates           373 k
Installing for dependencies:
  alsa-lib-devel          ppc        1.0.15-1.fc8     fedora            989 k

Transaction Summary
=============================================================================
Install      2 Package(s)
Update       0 Package(s)
Remove       0 Package(s)

What? It only needs alsa-lib-devel.ppc? So why has it been removed?

How can it be correct?
Are we sure yum is not fooled by the fact that the string "ppc" is contained in "ppc64"? Or 
something else?