Atari 5200 - Internal Differences Between The 5200 and The 400/800

Internal Differences Between The 5200 and The 400/800

Although the Atari 5200's internal design was extensively based on that of the 400/800 home computers, the differences were sufficient that games designed for one would not run directly on the other.

One of the most obvious differences was the 5200's lack of a keyboard. However, there were several others:

• The 400/800's 10 KB operating system was replaced with a simpler 2 KB BIOS, of which 1 KB is the built-in character set.
• A number of important registers, such as those of the GTIA and POKEY chips appear at different memory locations.
• The purpose of some registers changed slightly on the 5200.
• The 5200's analog joysticks appeared as pairs of paddles to the hardware, which required different input handling to the traditional digital joystick input on the 400/800.

Atari Corp.'s later XE Games System revisited the idea of a console based on the 400/800 hardware. However, as this was essentially just a 65XE computer with a detachable keyboard, it was able to run most of the home computer titles directly.