bill, thanks for the discussion of the AO node. irradiance caching is restricted to less than 100% due to its corresponding variable in the render properties called maxError (see poserpython methods manual). since maxError > 0, and since IC = 100*(1 - maxError), IC can't be 100%. apparently, trying to set maxError to 0 would require an infinite number of calculations per pixel for that part of the rendering calculation, similar to trying to set shading rate to 0 in all object properties as well as in the render settings.