[ESS] Startung up 64-bit R

[Kevin R. Coombes]

Hi,

I am running ESS version 13-05 with R version 3.0.1 on a 64-bit Windows 
7 Enterprise computer.

Several versions of R (currently 2.14, 2.15, and 3.0) are installed in 
locations like C:\R\R-3.0.1, so my .emacs file contains
   (setq ess-directory-containing-R "C:")
   (require 'ess-site)
When I use the command "M-x R" to start R from withing emacs, ESS 
successfully locates the 3.0.1 version of R, but it starts the 32-bit 
version rather than the 64-bit version by default.

Is there something else that I can or must set in order to persuade ESS 
to automatically start the 64-bit version of R instead of the 32-bit 
version?

(I can do this manually by defining a function that sets the value of 
"inferior-R-program-name" to the full, explicit path of the 64-bit 
version, but I would have to do this all over again every time I install 
a new version of R.)

Best,
     Kevin