• Namco used an earlier version on their System 11 boards from at least 1994 to 1995, they released an updated motherboard with retail chips on sometime after that. The games from 1996 onwards were coded to detect which version you had and switch. The games released in 1995 to 1995 ( only Tekken & Tekken 2 are known so far ) can only run on the early chipset, some parts of the software can cope but others can't. I would assume that they had been supplied with libraries later on that supported the final chips, but the game was too far into development to switch.
• Konami also used the same early version of the chipset on the arcade version of Crypt Killer.
• The main differences between the early and retail chips are the format of the GPU packets & an optional scrambled texture format. Currently I am guessing there is no texture cache and the scrambling allows it to fetch multiple pixels at once to make it fast enough.

(Many thanks to smf for submitting the above information)