After trying to run a variety of systems, it becomes clear that certain kernels are much smaller than others. In the past, I’ve tried several different versions of small memory Linux and BSD.
It becomes clear that the BSD kernel is the smallest of the three major flavors, and can run where nothing else can. PicoBSD can run in places that floppy-based Linux distributions couldn’t, and there are other instances as well. In trying to get Linux or UNIX running on the Compaq Armada E500 (with 128M), it became obvious to me that BSD is smaller than the Linux kernel or the Solaris kernel. Solaris appears to be the largest – running Solaris in 512M of memory (with KDE) is almost (but not quite) usable. Trying to install Fedora Core 5 failed as 128M of memory wasn’t enough to install it. Solaris 8 did run in 128M, but it is two versions out of date, and not really usable in that nothing current is available for it.
FreeBSD 6 works in 128M without trouble, despite being the most current version – where as Fedora and Solaris cannot run in that amount of memory. I should say, too, that this is, in all cases, with an X session running – whether WindowMaker (low memory) or KDE or GNOME (more memory).
So, if things are tight, best to go with BSD – whether with FreeBSD, NetBSD, or OpenBSD. And do yourself a favor and run WindowMaker….