Yup. I think most "diff" kind of programs works better if you could just put the file on ramdisk.
Most applications that expects large files will do memory mapped I/O even if your system has plenty of memory left unused. Moving the whole file to different region on RAM gives better performance.
I remember copying one of my VB6 project (the project is large, the built EXE file is about 12-15 MB in size, and build time is painful) to memory before compile will dramatically shorten the build time too.