Apple doubled the RAM in the iPhone 3GS taking it from 128MB to 256MB. Making it a killer gaming mobile. And when it came to the iPhone4, Apple proudly announced that this thing runs its own A4 processor that we first saw on the iPad. The A4 is known to have a clock speed of 1GHz and it certainly screams. But how about the RAM on the iPhone 4?
Well it turns out that Apple has packed in 512MB of ram in this beauty and this allows the iMovie, 720p video recording and multitasking to work just fine. The fact was actually confirmed by Apple during one of its developer sessions at WWDC. (Session 147, Advanced Performance Optimization on iPhone OS, pt 2).
This also justifies the lack of iMovie support for any previous iPod touch or iPhone, as the RAM just won’t do the trick and lack of multitasking in iPhone 2G and 3G as they have just 128MB of RAM.
Via Macrumors