Here's an older discussion. There are many more.

by R. Proffitt Moderator - 4/3/12 10:49 AM

In Reply to: ram drive by veilreaper88

http://serverfault.com/questions/259449/ramdisk-vs-build-in-io-caching-on-windows

This covers why a ramdisk (today) rarely wins. The disk IO is already cached in Windows (and in Linux!) so a pure ramdisk fails to deliver overall system gains because it would only be as good as you are at selecting some app to tweak it up for.

Besides my bet is the time spent implementing this would not be recovered.
Bob