Talk:MMC3

There's some documentation about the differences between MMC3 revisions here: [1] I'll add them in at some point, if nobody else does. --Drag 18:00, 19 April 2011 (UTC)

PRG RAM bank behavior

When PRG RAM is accessed via $6000-$7FFF, what does the MMC3 put on the upper PRG ROM address lines? --Tepples 23:24, 20 April 2011 (UTC)

Ideally, the MMC3 wouldn't put anything on the ROM address lines. :P Either way, if the CPU is accessing $6000-7FFF, I'd imagine whatever chip is selected would see %011xxxxx xxxxxxxx on its address lines. RAM would just see the x part, and whatever mapper-supplemented upper address lines if the RAM is bankswitched. --Drag 04:05, 21 April 2011 (UTC)

When I hear "wouldn't put anything", I think "high impedance". It appears you claim that if $6000-$7FFF is accessed, the PRG A13 through PRG A18 outputs from the mapper are high-Z, not the value in either PRG bank register. Do I misunderstand? --Tepples 22:42, 21 April 2011 (UTC)

The simplest thing electrically is to never disable the address drivers. Given how MMC3 works I'd guess it drives the upper address lines high. Lidnariq 18:08, 22 April 2011 (UTC)