Hitting the Ubuntu Natty repository is an fglrx-installer 8.840-0ubuntu1 package, which can be viewed on Launchpad. The publicly released Catalyst 11.3 driver from yesterday is based on the fglrx 8.83 release stream, which puts this fglrx 8.84 driver as a pre-release of Catalyst 11.4. This is interesting as what I said yesterday is that it will not be until Catalyst 11.5 in May when xorg-server 1.10 ABI support officially arrives, so AMD must have back-ported the changes to Catalyst 11.4 either as a special build for Canonical or maybe users of other Linux distributions will see this support next month too.
The Debian change-log simply mentions "New upstream release 8.84.6." This proprietary AMD driver for Radeon / FirePro graphics cards is compatible with xorg-server 1.10 and also the Linux 2.6.38 kernel as found in Ubuntu 11.04.
As AMD has seeded Canonical with driver pre-releases rather than only back-porting the kernel/xorg-server changes to the current release stream, past Catalyst-for-Ubuntu drops in the past have yielded some surprises for users. Some of the releases picked up early have yielded notable bug-fixes and/or new features.
Is there any features to be found in this early Catalyst 11.4 driver update? Yes, there is. The libGL and libglx libraries have been renamed to fglrx-libGL and fglrx-libglx. Why? Dynamic switching support. In looking at the package that was provided to Canonical, there is support for switchable graphics! For notebooks with AMD and Intel graphics!
For those with notebooks that have a dedicated AMD GPU and Intel IGP, this can allow you to switch between graphics processors. Though due to current limitations of the X.Org Server, the X Server must be restarted when switching. At that point, the libGL library will also be redirected to the appropriate OpenGL library so that there is correct OpenGL rendering support. This is Linux support for AMD's PowerXpress feature. I'll talk more about this feature finally implemented under Linux shortly.
For those hoping to use this new driver on another Linux distribution, from Launchpad there is the "fglrx-installer_8.840.orig.tar.gz" file, but it's not the complete installer. There aren't the binaries for older xorg-server releases, etc. Depending upon the distribution you're looking to bring up the fglrx 8.84 pre-release on, it may or may not work.