nesdev.com

I'm trying to find what 6000-7FFF RAM is used for.

From this link:

https://wiki.nesdev.com/w/index.php/CPU_memory_map

I see it's "Battery Backed Save or Work RAM"

I'm working with Mega Man 4, so I guess it's work RAM.

Does it means it's RAM where stuff is stored now and then? If so what is the different with 0-7FF RAM? Since 0-7FF RAM can be used for this too.

Depends on the physical cartridge.

In most games, there's nothing there at all. No RAM, no battery. Writes are ignored, and reads return "open bus".

In a bunch of games, there's an 8 KiB RAM on the cart. Most of them (but not all) also have a battery to allow the RAM contents to hold save games.

In a small handful of games, there's a smaller amount of RAM (e.g. 5 KiB, 2 KiB, or 128 B) in some smaller section of that range.

Thanks!!

So in Mega Man 4 there are reads there, so it means I have lots of RAM there I can use?

I would assume the preexisting game is using all of it until such time as you can establish that there are regions of memory that it is not using.

I played it a bit. It didn't read or write to 6000-7fff for me.

Bootgod is down, but the cached page says nothing is there.

However, an emulator doesn't know that. You should be able to use that space and pretend like there is a RAM chip there.

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You are correct, I use a version with a patch from PureSave and I realised he wrote datas there.

Thanks!!

yea it's just basically like more RAM you can use for whatever, like the 0-7FF stuff.

I do it for both types things on megaman odyssey. i use 6000-62FF for "saved game" progress stuff, since i have "save games" not passwords.

and 6300-7FFF is an entire level (from the ROM loaded into RAM)

Where i can freely modify anything about a level you want, directly while your actually playing the level, like delete/add level building blocks, update palettes (more than MegaFLE originally lets you do in the megaman 3-6), etc etc

pretty sure Rockman 4 Minus Infinity does the very same thing (loading an entire level into RAM, to modify it "anytime anywhere"

Thanks a lot for the answer!!

I'm not sure I quite understand, the level is written on the PPU memory... can't you just modify it anyway with the PPU? Since you will need to send it to the PPU anyway.

Could you also put Odyssey on a Nes Cartdrige?

I'd say his level spans several screens, like in a megaman game.

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dont know if that last reply was to me, or dougeff, but...
I never mentioned anything at all about PPU stuff. I dont know how to deal with CHR-RAM stuff. (mm4 and 6)

I was talking about putting things in the 6000-7FFF RAM that you originally mentioned.

and i cant say for sure how well my game would work on a "real" NES, but it'd have to be a an actual real MMC5 cart the same as 4 MI was.

Thx I've got my answer from yours and nesrocks. What I was meaning about PPu is that your screen you put in 6000-8000 is actually gonna be sent to the PPU somehow at some point to be drawn on screen, but nesrocks answer solve this mystery for me.

Which MMC5 features does use? Just 1 MB PRG ROM? Or does it also use independent $8000 and $C000 switching, WRAM switching, ExGrafix, multiplier, or anything else not common in other mappers?

I honestly don't know how to find the answer to that question?