Xash3D reads the wad file headers, maps the texture offsets, and uploads them to the GPU. However, unlike vanilla GoldSrc (which struggles with memory management when loading too many WADs), Xash3D implements a smarter caching mechanism. It can handle high-resolution texture replacements more efficiently, supporting formats like PNG and TGA for external "hires" texture folders that vanilla GoldSrc often ignores or scales incorrectly.