Hi all; I have a 3GS that I got July 7/09 and as I've upgraded OIS to the latest I've noticed that it really lags. It is so slow searching for words in dictionary or places in google maps or google searches that I some times feel it is broken. Does anyone have similar experiences and/or does anybody have a fix or workaround for this problem?
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I am currently running iOS 5.1 on my iPhone 3GS. First, try doing a hard reset by holding the Home and Sleep/Wake buttons simultaneously until the Apple logo appears. A key thing I've noticed is that iOS 5 on the 3GS can't handle a lot of apps running in the background. So periodically double-click the home button and close any apps you're not using. Second, disable Spotlight search. Personally, I don't use it at all and it requires the phone to index files and apps. To disable it, go to Settings > General > Spotlight Search > uncheck any or all the unnecessary items you don't need your iPhone to index. Thirdly, make sure to have more than 500mb of free space on your iphone; running your phone at or near full capacity will definitely slow things down.
If performance issues persist, I recommend performing a restore via iTunes and not applying your backup file. Start fresh, wipe your iPhone clean. Your backup file may contain errors and/or items formatted for the iOS 4.x which may prove problematic.