"PUD is a Chinese distro based on Ubuntu 7.04 (Feisty) and the 2.6.20 kernel. They've patched in several filesystems and through using SquashFS for the loader filesystem, the ISO is a mere 193megs.
"I was going to do the full test of PUD on my ancient laptop (PIII 1gHz, 256megs of ram) but there was one problem: WiFi drivers. The PCMCIA card that does this is supported natively in Ubuntu--since 6.10--but try as I might, nothing could get a response out of it in. So to cut a long story short, I've been testing this on a 3gHz P4 with 768 megs of RAM..."
