Excellent question, one I don't have a complete answer for since I've never tried it. Why not load the whole operating system and all the data a person would ever use in there as well? Knoppix has a boot option which allows you to copy all the iso files into RAM. Grab the DVD, boot it toram(if possible on DVD), install WoW into home; that should be about 20GB. When I look at this situation I wonder what is happening on the Front Side Bus and how much of the important data is getting down the channels ahead of non-important. DSL is a derivative of knoppix with the same boot option and when it is booted toram there is still lag due to 100% cpu; Moore's law if you will. How much of the cpu usage is user instructions or system duties like memory management. Filling the tables with pointers to dormant data would increase the Big "O" and place even more demand on an already taped out tech.

Looking at a Motherboard we see it is covered in circuits. For the machine to be operating at 100% efficiency, all the circuits should be pulsing with data simultaneously. The MPU should be at 100% as well as cache memory. One way of side stepping Moore's Law is multitasking the hardware better and increasing bandwidth. Offloading common operations onto hardcoded processors with a direct connection to main cpu and system bus, etc.. But I digress, the most important reason to do this is as a means of upgrading an old computer at low expense. I highly recommend trying to run DSL on an older cpu, it seems the world needed better software a lot more then faster processor speeds. Older machines can act as Firewall/Router/Gateways, web servers, tor servers, file servers, wireless monitors, etc.. Don't sell or throw away that xbox because it has many years left running the latest kernel code.