iPhone 4G Processor Revealed: Same as iPad writes:
Today’s photos from Vietnam of a leaked iPhone 4G prototype contain legible part numbers revealing new iPhone’s processor: the Apple A4.

The silkscreen on the production A4 reads:

* APL0398 339S0084 YNL215X0
* K4X2G643GE N26CGM0T

Our engineers are not surprised by this finding. We were very impressed by the extraordinarily low power consumption of the iPad, and remarked at the time that its power consumption and board design was much more in line with handheld devices than laptop computers.