Talk:CNROM

Bankswitching and $2007 reads

I wonder if this info is any useful, especially the second sentence :

Many CNROM games such as Milon's Secret Castle store data tables in otherwise unused portions of CHR ROM and access them through $2007 reads. If an emulator can show the title screen of the NROM game Super Mario Bros., but CNROM games don't work, the emulator's $2007 readback is likely failing to consider CHR ROM bankswitching.

The technique to read non-graphics data from CHR ROM is of course worth mentioning, there's no doubt about that, but I don't feel like this is the right page to mention it, as it has nothing to do with CNROM / mapper 3 itself, in fact games using all kind of mappers does that (Super Mario Bros (NROM), Tiny Toons Adventure 2 (MMC3), Batman - Return of the Joker (FME-7), etc....) This should be mentioned on a page which deals directly with CHR-ROM or something.

As for emulators where the title screen of SMB works, and that Milon's Secret Castle doesn't work, well how many of them there are ? I really see zero pertinence in this sentence. Bregalad (talk) 01:40, 5 May 2014 (MDT)

People tend to implement the simpler mappers first, so they're more likely to collide with this failure mode while implementing NROM and CNROM long before they could notice it with MMC3 or FME7. I can see an argument that the information belongs only in Tricky-to-emulate games, but it fits very nicely in the lede here, and Tricky-to-emulate games is a poorly-organized info dump... —Lidnariq (talk) 03:20, 5 May 2014 (MDT)

I understand, but what is emu-dev stuff doing just below the headline of a mapper/hardware page ? I'm not saying the info is useless, just that it is out of place. The fact another page is a poorly-organized info dump is not an excuse to leave info that doesn't belong to here here.Bregalad (talk) 04:03, 5 May 2014 (MDT)

Security Diodes

About the security diodes, I noticed that a Japanese Gradius board have slot for 4 diodes instead of 2 (but only 2 are used). Also, some NES-NROM boards have slots for diodes too. Surprisingly, many non-Nintendo made boards cloning the CNROM mapper (Konami, Taito, Bandai) also have those same diodes. Considering how few sense those makes, it's very surprising they would all use them, isn't it ? Bregalad (talk) 01:40, 5 May 2014 (MDT)

I can't think of a context in which diodes could be useful on an NROM board... do you have a photo somewhere (e.g. NesCartDB) ? —Lidnariq (talk) 03:20, 5 May 2014 (MDT)

I also can't think of where they could be useful (not that they are useful on CNROM either...) but NES-NROM-xxx-02 and NES-NROM-xxx-03 boards have slots for 2 diodes next to the CIC. I don't have any game using one of those boards so I can't check where they connect, but you can see the slot clearly on the NesCartDB. Bregalad (talk) 04:03, 5 May 2014 (MDT)