Hitachi 6309 definition processor
's version of the Motorola 6809 microprocessor
. Compatible with the 6809, it added two new eight-bit registers
that could be added to form a second 16-bit register, and all four eight-bit registers could form a 32-bit register. It also featured division, and some 32-bit arithmetic and was generally 30% faster in native mode. This information, surprisingly, was never published by Hitachi.
Technical reference (http://sandelman.ottawa.on.ca/People/Alan_DeKok/interests/6309.techref).