Most accurate timing?

"Duncan" == Duncan Murdoch <murdoch at stats.uwo.ca>
    on Mon, 01 Aug 2005 08:48:39 -0400 writes:

    Duncan> For a graphics display, I'd like a high resolution
    Duncan> timer, something like Sys.time(), but it is only
    Duncan> accurate to a second.  Is there a clock in R that
    Duncan> gives a finer value?

Why can't use  proc.time()  ?

It's help file says

     The resolution of the times will be system-specific; it is
     common for them to be recorded to of the order of 1/100
     second, and elapsed time is rounded to the nearest 1/100.