If you look at my earlier post in this thread. I did 3 tests renders:

I rendered a scene three times: first using the Vue 8 OpenGL 2.1 setting, then the Hardware one and then Vue 7.5 OpenGL hardware, also. I was looking for memory start and finish and rendering times. I used a 1600 x 1200 format and User Render setting, low enough to do htis in a reasonable time, but not too low.

The times respectivally were 3hrs 35mins 37secs; 3hrs 35mins 4secs, and for the Vue 7.5 3hrs 25mins 33secs. These images were initially created in Vue 7.5 and then brought into Vue 8. Otherwise there would be no way to compare. Notice that there was little difference. The scene contained a lot of clouds and an ecosystem.
RE: Resources Vue 8 OpenGL2.1 started at 85% ended at 83%
                             Vue 8 fixed harware pipeline  started at 90% ended at 88%
                              Vue 7.5 Hardware acceleratedstarted at 90% ended at 88%

I don't think this is 6 times higher. These were very controlled tests.