Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
At the end of 2009 I published benchmarks comparing Ubuntu's 32-bit, 32-bit PAE, and 64-bit Linux kernels. Those tests were carried out to show the performance impact of using 32-bit with PAE (Physical Address Extension) support, which on the plus side allows up to 64GB of system memory to be addressable from 32-bit machines, but is still significantly slower than a 64-bit kernel and user-space. In this article the tests have been carried out on modern hardware and with the latest Ubuntu 11.04 packages to see how the three kernel variants are performing in 2011.
While nearly all desktop/notebook hardware shipping has been 64-bit capable for some time, Canonical continues pushing Ubuntu 32-bit as the "recommended" version of Ubuntu. 64-bit Linux itself and nearly all major open-source programs have been in great x86_64 shape for years, but Canonical is likely still recommending 32-bit Ubuntu for the few binary-only programs out there that work better in a 32-bit environment, namely Adobe Flash and the Java web plug-in. There are 64-bit plug-ins available, but they are not generally updated at the same pace as the 32-bit version, for example. There are also open-source alternatives such as Lightspark and Gnash that natively support i686, x86_64, and even other architectures too. So it is becoming somewhat odd that Canonical is still pushing 32-bit Ubuntu over the 64-bit version even when they still will not ship Adobe Flash and other binary blobs by default so that they can remain a free software distribution.