KDE 4 works well with 256 MiB of memory and 1 GHz CPU

"I decided to boot my Thinkpad X60 with "mem=256M maxcpus=1", logged into KDE 4 and set the power saving policy to "Powersave", which throttles the CPU to 1Ghz and locks it there. And then I used KDE 4 some, started Konqueror, browsed about a bit, configured a few things with System Settings, started Kopete and chatted a little."