I was wondering how he prevented the kernel from caching the disk blocks in memory, but then I saw he is running it on a machine with 4MB of main memory, and presumably most of that is eaten up by the TCP stack, web server, and parallel ethernet drivers. Not to mention memory needed by the OS itself.

Even more surprising, his page isn't just pretty, it is functional! You can get a copy of the demo for Wolfenstein 3D off of the site (supposedly, I did not try).