write() is delayed on Windows

I am running my program on Windows 7 and I noticed some delay when I use the write() function.  The write() function would take some time to return. This happens with Ruby 1.9.3 and 2.2, but this does not happen with Ruby 1.8.7.  Also, I noticed if I have an Acrobat pdf file opened in the background, then the delay does not occur, the write() function would return immediately.
