NFS-RAMBOOT adapts my RAMBOOT hack to NFS root (PXE or not). On boot, it extracts an OS tarball from an nfs share into local RAM (recommended 3+GB of RAM). The result is like a very fast SSD.
Why do this? Compared to RAMBOOT, loading (and saving) the OS tarball over gigabit ethernet can be faster than a local hard drive or USB drive, if the file server has an SSD or a faster hard drive (compare 3.5" drives to 2.5" laptop drives, for example). Also, having the OS tarballs...