Checklist for Cleaning Up Drivers

Over the past year(s), Aaron has done some driver "cleanup" work. This generally involves picking apart a driver, revisiting all the assumptions using whatever information is available, and updating it to take advantage of newer features in MAME that have been introduced since it was first written. To do this work, Aaron keeps a checklist of things to do, just to make sure all bases are covered. This list is constantly updated, but since it is a good set of guidelines for updating a driver, or writing a new one from scratch, it is provided here.

Timing/interrupts:

• all crystals on the PCB documented via #defines
• all CPU and sound clocks derived from #defined crystal values
• re-verify interrupt generation timing and sources
• implement interrupt acknowledges (many older drivers didn't bother)
• add accurate watchdog durations

Memory:

• unified read/write memory maps (they used to be separate)
• map the entire address space fully, if possible from schematics
• use AM_SHARE where appropriate (better than sharedram read/write handlers)
• convert memory banking to the new system (memory_configure_bank)
• use address_map_bank_device for banking RAM or peripherals over ROM

Graphics:

• gfx layouts should use RGN_FRAC wherever possible instead of hard-coded values
• gfx layouts that are common should be shared (vidhrdw/generic.c)
• accurate hblank/vblank/visible areas, derived from schematics if possible
• convert from old macros to new screen macros for display info
• use new more accurate screen timing routines for H/V positions
• convert to tilemaps, if applicable
• change to use resistors for palette generation
• add limits on sprite drawing (e.g., how many per scanline), if known

Inputs/Outputs:

• convert non-DIP configurations to configs
• use PORT_CUSTOM where appropriate instead of memory overrides
• connect coin counters (often missing)
• connect hopper output and feedback for betting games (payout buttons usually cause errors if this is not done)
• connect PCB outputs via the new output system
• add DIPLOCATIONS
• verify DIPs and inputs

ROMs:

• memory regions reduced to minimum size (they don't have to cover the whole address space; note that AM_REGION makes this possible with CPU types like 6502, 6809 and x86 on which execution has to start from near the end of addressable memory)
• make sure ROM names are good and accurate to what we know
• check for any unemulated clones

General:

• update source files to be in order: header, includes, constants, typedefs, macros, globals, inlines, code
• update driver file to be in the same order, followed by: address maps, input ports, graphics definitions, sound configs, machine driver, ROMs, driver init code, drivers
• add save state support
• move all globals to hang off of driver_data
• de-obfuscate the code where it is confusing

Some recent driver updates that are pretty up to date include: ccastles.c, cloud9.c, missile.c, turbo.c, zaxxon.c.