Set your bucket at 64 to start. Let P6,7 lower it as needed 0n auto (EDIT>General prefs>Misc tab>check Adaptive threshold) Just below is the controler you seek. I've never messed with it. Chances are, you have exceeded the memory limit of your pc. You did not say how much you have total. It can be exceeded with a hi res head in the viewer and/ or with unrealistic rendersettings. I would leave dpi settings at default until you resolve a render(dpi is for printersettings only). I would turn off anythging you are not sure about elsewhere too (DOF ot texture filtering... ). Shading rate is a renderkiller(dropping by 1.00 = 100x calculations per pixel) Ray Trace bounces too (less is better) Pixel samples (less is better. 2-3 for closeups, 3-5 for full figure) Your lights may be the culprit too... What are the bias settings? As adp001 stated,, each shadowmap is stored in memory. RayTrace lights are "lighter" on resourses. Set bounces to 0 if you are not using reflect, refract. Better to start low and work your way up. Save before you render, too...