I was being inexact since I didn't feel like refreshing myself on the specifics. Just wanted to communicate to zero that cup size depends on other factors that go beyond just what is in the cups.
I recently tried adding a 2nd GTX 670 4GB. I booted up with the new card once by itself to make sure it worked, then I added the other card and restarted with the sli bridge. Everything appeared okay in device manager, both cards showed up in nV control panel and I was able to enable sli...