Can't you render to an imagebuffer that's larger than the screen? Like:
ImageBuffer = CreateImage(800,800)
SetBuffer ImageBuffer
RenderWorld
SetBuffer BackBuffer
DrawImage Imagebuffer, 0,-200,
Flip
ImageBuffer = CreateImage(800,800)
SetBuffer ImageBuffer
RenderWorld
SetBuffer BackBuffer
DrawImage Imagebuffer, 0,-200,
Flip