But i heard that memory only helps you to open more programs and not to speed up. So let's say my program and rendering with it takes just under my total memory .

like say i have 4GB and my OS takes some and Poser  takes 3.5GB. that means it's still using RAM so even if you added more ram it would use 3.5GB thus it would be a waste having bought more RAM.

am i wrong? i'm just saying stuff i don't know how it works.