In 1965, Kodak released Super 8 technology with the intention of replacing the original 8mm format. Adding a pressure plate to Super 8 film cartridges was supposed to make this format generally more stable than its predecessor, and allowing a larger image size increased overall clarity.
While the standard 8mm filming process takes film that is actually 16mm wide and runs it through the camera twice, Super 8 film is 8mm wide and boasts smaller sprocket holes--which allows more surface area for images.
While Super 8's larger image size offers improved resolution, taking the pressure plate from the camera's gate (a la standard 8mm) and adding it to the film cartridges has not proven to make operation more stable. Some, in fact, argue that it does exactly the opposite.
Standard 8mm film can be wound backward through the camera and re-run to achieve a unique double-exposure effect. Because of its cartridge-based format, Super 8 doesn't offer the same perk.
Though other varieties of Super 8 film are still available as of 2009, Kodak announced in June 2009 that it would soon end production of KODACHROME film after 74 years.