Somebody decided that it would be funny to design the Ubuntu Lucid (and newer) Arm version to run only on the Arm A8 with Thumb2 instruction set. The problem is that the N900, one of the only Arm A8 devices in general distribution, has a buggy Thumb2 implementation. This means that Ubuntu versions higher than Karmic are unstable and crash-prone on the N900.

There are two big ironies with this decision by Canonical.

First, the Thumb2 instruction set has only one purpose, to make the binaries smaller. It has no effect on speed. Yet, any device capable of running the binaries included with Ubuntu will have plenty of space in its rootfs, at least enough for a full Ubuntu system (if it doesn't it can easily use tricks to get around that limitation, like the N900 uses). So the Thumb2 instruction set is really useless on A8 devices.

The second big irony is that they insisted on the useless Thumb2 instruction set, but refused to use the VFP optimisations (things that would actually improve the speed of the apps, and actually supported on the N900) because they didn't want to limit themselves too much on their choice of devices. WTF?! Thumb2 isn't limiting your choice of devices, but VFP optimisations somehow is limiting?!

Argh!