yeah, that is just a specific h/w capability of the carmine ... you can simulate this by attaching to the main display, 
creating another surface of same stride, width and height, then use gf_draw_blit2() and send a copy to your screen.  I 
would waiting for hardware idle before doing so.  You can then populate a img_t, and call img_write() if you want to go 
that far - data from gf_surface_get_info() using your secondary surface.