The Wiki article[1] suggests a far more interesting story than better fab technology- Apparently these puppies have an ARM core emulating the original processor

The Wiki article[1] suggests a far more interesting story than better fab technology- Apparently these puppies have an ARM core emulating the original processor and operating system, making it possible to build custom firmware if you are so inclined. [1] http://en.wikipedia.org/wiki/HP-10C_series#HP-15C http://en.wikipedia.org/wiki/HP-10C_series#HP-15C