He says shadow atlas explicitly use GL_DEPTH_COMPONENT16 texture of 4096x4096, not GL_DEPTH_COMPONENT24 or 32. Isn't by using 16 he expects lower buffer/memory usage and radeon just mapped that as 32
Not really a bug, more of a missing feature. llvmpipe obviously has no memory restrictions, but discrete gpus only let the cpu access 256mb. If you create a 512mb texture, how exactly would you upload data to it when you cannot access it all?
Ie, it would require additional code to split uploads in several pieces.