At the preferences menu in Vegas Pro 8.0a it only allows a maximum of 4 rendering threads.
Does this mean that a two quad processor computer with 8 computing cores will be wasting the second processor ?
Well, literally, no the computer will not be wasting the other 4 cores since they'll be open for use by the couple of hundred other threads running on the computer, including Vegas's own 40+ non rendering threads.
But if Vegas can only run 4 render threads then the best you can do is open up vegas a second time and work on another project.
. Open Vegas
. Click on OPTIONS and, with SHIFT Key pressed, click on PREFERENCES
. The Preferences Windows will open and you could see the INTERNAL TAB, click on it
. In the white box write "threads", you'll see "MAXIMUM VIDEO RENDER THREADS" and the value "4"
. Modify 4 with 8 (or other) and try to work with Vegas to see if there are improvments