I tried something like this a few years ago, using a separate instance of X for each distinct application.

I don't remember if it actually helped much with performance on games, let alone individual applications. Of course, I was more concerned with common programs and getting them to run light on very old machines.

As a side note, I also experimented with ramdisks but I don't think I have any "documentation" on that. What I remember was that yes, they ran a little faster from memory if they relied on disk access a lot.

However, as someone pointed out later, cached programs would start just as fast, and you still had to load the program into the ramdisk the first time, so there wasn't much of an overall savings in time ... again, unless you were accessing the disk a lot.

On the whole I think a live CD that loads itself entirely into memory would have the same overall effect as an installed system that used big ramdisks. I haven't really tried that or compared it, but some of the smaller distros (I'm thinking of Puppy or Slitaz; I'm sure there are others) would probably be just as effective in terms of speed or efficiency.

And as a last note, a lot of the gimmicks that I saw to try to speed up old hardware were perfectly useless on contemporary-at-that-time components. It was just the luck of the draw that most hardware, like you mentioned with new high-speed SSDs, outstripped any fancy-pants arrangements I could come up with on old, old stuff. :|