After the launch of the iPad 3, Apple dropped the price of the iPad 2 to $399. It turns out that it made some other changes to the device as well, notes AnandTech.
Although the iPad 2,1 and its 3G brethren all used a 45nm Apple A5 SoC, the iPad 2,4 uses a die-shrunk 32nm version. The performance remains the same, but the die is much smaller. This isn't however just a normal die shrink, as Apple is using Samsung's 32nm high-k + metal gate LP transistors for this new A5 die. Intel was first to make the HK+MG transition back at 45nm in 2007 and correctly predicted that no one else would make the move until 32nm at the earliest.
By switching to the new SoC for the iPad 2,4 Apple gets lower manufacturing costs and experience with Samsung's 32nm HK+MG process which will eventually be used in much higher volumes.
In addition, the new SoC also brings the added benefit of improved battery life!
Remember the basics of Samsung's 32nm HK+MG process: a 40% performance improvement at the same leakage, or a 10x reduction in leakage at the same switching speed. As the iPad 2,4 retains the same clocks as the initial iPad 2, the benefit realized is a significant reduction in leakage current. This translates to tangibly better battery life.
AnandTech's testing found that the new iPad 2,4 provided over two hours of additional battery life when playing back video and 1.6 additional hours when browsing the web. This is a significant increase over the previous iPad models. Unfortunately, there doesn't seem to be a way of determining which iPad model you're purchasing.
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