I got this computer without power supply or software. I took a 400/800 power supply and it worked, and I was also able to use 400/800 carts in this system. As I understand it, the 1200XL was the first of the new generation of Atari computers. The 1200XL was followed in 1984 by the 600XL and 800XL. The XL models appear to be refreshes of the original 400/800 models with formerly optional equipment built in (16k, 48k, 64k). Performance-wise they're basically the same. Atari and Apple in 1983 felt the need to keep up with Commodore by offering something new, even if only cosmetic.