I open a big assembly and the realview graphis option is grey-out - is there a way to enable it
That depends on whether your graphics card/driver are able to support realview. Also, make sure that large assembly mode isn't active. You can tell by looking at the bottom of your screen. If it is, go to Tools->Large Assembly Mode to turn it off.
... or just raise the threshold.
actually, the video card supports this feature - just turn off the large assembly mode did the trick
Retrieving data ...