Well, look at that. The newest batch of leaked 4G iPhone photos includes crystal-clear* tear down shots, and one of them reveals what seems to be Apple's own A4 processor. Engadget notes that "339S0084," seen just below the Apple logo, identifies what we're looking at as the A4, according to Chipworks.
The A4 is the Apple-designed system-on-a-chip (SoC) that's manufactured by Samsung and currently used in the iPad. Nearly everyone who touches an iPad remarks on how snappy and responsive it is. Here's hoping that the next iPhone offers similar performance -- and prolonged battery life -- with this thing under the hood.
Engadget further points out that "APL0398" also appears on the chip that's inside the iPad. As for the other markings, well, we don't know what they indicate. We'll let you know if we find out.
*This one's blurry because I blew it up a bit to show the text on the chip.