Like the South Korean and European models, the North American 80 GB (2007) model also excludes the PlayStation 2 "Emotion Engine" CPU chip.[76] However, it still keeps the "Graphics Synthesizer" GPU.[81] Due to the elimination of the "Emotion Engine", the level of compatibility was reduced.[76] The 40 GB, 80 GB (2008), and 160 GB models have two USB ports instead of the four USB ports on other models, and do not include multiple flash card readers, SACD support,[82] or any backwards compatibility with PlayStation 2 games.[19][76] This was due to the removal of "Graphics Synthesizer" GPU, which stripped the units of all PlayStation 2 based hardware.