Apple is looking into reports that its iOS 4 does not run well on older devices such as the iPhone 3G and 3GS. To be sure, Apple has warned from the beginning that not all of the features -- in particular, the multitasking in iOS 4 -- could be supported on older devices. However, owners of those phones have found that upgrading resulted in problems more extreme than the lack of new features. Most of the complaints center on devices that slow down to the point where they are barely functional.