Smart Cards: An Introduction - The ICC and Harvard Architecture (
Page 3 of 9 )
The ICC itself
The ICC cards usually employ a low power micro-controller like Intel® 8051 or
AVRs from ATMEL® as the core CPU with the clock frequency up to 5 MHz or so.
These micro-controllers are available in 8, 16 or 32 bit flavors. Basically the
decision is governed by the requirements of the applications the card needs to
support.
The architecture of these CPUs varies as I mentioned above. The Intel uses
the Von Neumann architecture where as the AVRs from ATMEL use the Harvard
architecture.

Figure 3: The Harvard Architecture
(Source:
http://www.ee.nmt.edu/~rison/ee308_spr99/supp/990119/harvard.gif)
Also some ICCs also use two CPUs just to enhance their capabilities. For
providing advanced security features such as using RSA for cryptography much
more processing power is required so this is provided the help of these special
purpose co-processors. The ICCs with these chips are expensive as compared to
single chip ICCs.