What Bwang said. Plus you won't get flickering when stuff moves around (and needs to be erased to do so). I don't know how Nspire ASM/C compares to 83+ Axe, but on 83+ Axe, inverting the entire screen bit by bit takes about 20-30 seconds for 6144 pixels if you draw directly to the LCD. When storing to the buffer then only updating the screen once everything is done, it took about half a second.