Hi Roger.
Yes, Vegas uses only the CPU. However, some people want/need more power, and the “Divide.Frame” plug in costs $95US. It is supposed to re-route some of the computational processes to the graphics card, thereby ‘tapping’ the power of the graphics card. It might be cheaper for some to slap in a hot video card, than replace.
I have not used Divide.Frame. Someone mentioned it several months ago, and at that time it was ‘try before you buy’, but they mention having worked out some bugs in Vegas on the main page.
https://www.divideframe.com/
I am hoping that someone who has used it will let us know. 🙂
Norman Willis
http://www.nazareneisrael.org