The A5 processor has 512 MB RAM, just like the processor in the latest iPod Touch.

How do we know? The package markings E4064P3PM-8D-5 indicate the A5 has two 2 Gb, LP DDR2 RAM dies inside, according to Chipworks.

These die photos from Chipworks shows the inner workings of the A5. Care to see the die in all its gory glory? Check out the high-res version.