Currently running 4.4 with latest updates, Pi 3 b+

I'm resurrecting this topic because this doesn't seem to work anymore. I put mame2003-cheats = "enabled" into retroarch-core-options.cfg but no 8-way movement.

This WAS working last year so some change has been made to mame2003 since. Can we please put this back the way it was? I don't think anyone here wants to have to use mame4all.

Yes, the method to make two-handed "tank" controls work on a single 8-way joystick does not require any cheats, just a clever set of controls mapped to what is sometimes called a "tankstick". The mapping makes use of <CODE_NOT> logic where you are actually excluding certain input combinations. MAME lets you setup mappings like this by using a double-tap of an input while in the GUI menu which changes it to a <NOT>, so if you do several inputs in rapid succession, before MAME accepts an entry, you can make some combinations that work in interesting ways.

Here's a mapping for a single 8-way joystick to control two tank sticks like Battlezone:

Game Control Mapped to Right/Up Up <not> Right or Left <not> Down Right/Down Down <not> Right or Right <not> Up <not> Down Left/Up Up <not> Left or Right <not> Down Left/Down Down <not> Left or Left <not> Up <not> Down

There is an odd situation for Keyboard controller users in lr-mame2003 that requires you to first set all retroarch inputs to NUL using a per-rom config file if you want to do this. You can read about it here.