Looks like today's morning's firmware leak turned up some well hidden details about the iPhone's hardware engine -- and also confirming some reports we'd previously received. From what we can tell, it looks like the iPhone's got a 620MHz ARM chip running under the hood. Specifics:

• ARM1176JZF chip with TrustZone (enables trusted computing environment for media, apps, network, OS, etc. -- very bad for hackers)
• Can vary in clock speed up to 700MHz or more, depending on implementation (thanks, Nigma)
  
  
• ARM Intelligent Energy Manager (claimed to reduce power consumption 25-50% in portables)
• 16K / 16K cache
• Features vector floating point coprocessor ("for embedded 3D-graphics")
• ARM Jazelle enabled for embedded Java execution (hmm...)
• SIMD, high perf integer CPU (8-stage pipeline, 675 Dhrystone, 2.1 MIPS)
• 0.45 mW/MHz power draw (with cache)

Whatever it is Apple's got that thing doing, they're doing it right. Thus far our iPhone battery life tests have far exceeded expectations (more on that soon).

Update: Sascha at Gear Log seems to think given the recently discovered Samsung chip in the iPhone, perhaps the processor in question is a Samsung S3C6400, a recently-produced 667MHz ARM1176JZF-based CPU that seems to fit the bill.