This blog is updated daily.
A general description is here.
(Windows only) If both 32 and 64 bit versions of R are installed, the ‘bin/R.exe’ and ‘bin/Rscript.exe’ executables now run 64 bit R. (To run 32 bit R, overwrite these files with copies of ‘bin/i386/Rfe.exe’.)
(Windows only) If a user chose to install 64 bit R but not 32 bit R, the ‘bin/R’ and ‘bin/Rscript’ executables failed to run. (PR#15981)