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 Post subject: mmc3 vs mmc5
PostPosted: Sun Dec 09, 2018 8:26 am 
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There has been a lot of research on MMC5 recently that it got me interested to know more on the subject since I'm curious, like always. I started to read the wiki to know the features but there is a few part I'm not sure what you can do. For now, what I'm trying to look for is what is the mmc5 can do or do better compared to mmc3?

From the wiki I can find this:

- vertical split
- more rom space for chr/prg (1024k)
? but for chr, if set in 1k mode, can you access all of it? (didn't read enough yet to figure it out)
- prg, many mode and can set all of them in 8k and be switched (yay)
? what is the default bank then? I guess the last one is set at $D000.
- you can use ram for name table to make it more colorful (oohhh, shiny)
- a lot of ram, if wanted (up to 128k)
- extra audio (famicom only)
- I guess there is no mapper equivalent yet for creating you own cart, if interested to make carts

Did I miss anything? What I'm curious is what happens when set in 1k mode with 1024k. Need to read more the wiki but didn't find it yet.

Will continue to read the wiki :D


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 Post subject: Re: mmc3 vs mmc5
PostPosted: Sun Dec 09, 2018 8:34 am 
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You missed a lot. Just read more about the MMC5. I don't see the point of this thread if you haven't already researched the MMC5 much by yourself, but there's obviously a lot it can do the MMC3 can't. I don't think it is our role to tell you again what has already been said in docs and the wiki, unless there's something in particular you don't understand.

  • ExGraphics mode
  • Third nametable if not using the ExGraphics mode
  • Better scanline counter
  • Hardware multiplier
  • Much more fine CHR switching; 12 1kb banks instead of 4 1kb banks and 2 2kb banks (all 512 tiles are usable for 8x16 sprites regardless of BG)

And yes you can access all CHR in large ROMs even in 1kb banks, the upper bits are selected with the $5130 register. Unfortunately the wiki was edited a lot recently by MMC5 reverse-engineers, and not always for the better when it comes at epxlaining things clearly... this will eventually be fixed but needs some time.


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 Post subject: Re: mmc3 vs mmc5
PostPosted: Sun Dec 09, 2018 9:13 am 
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Bregalad wrote:
Unfortunately the wiki was edited a lot recently by MMC5 reverse-engineers, and not always for the better when it comes at epxlaining things clearly... this will eventually be fixed but needs some time.


Then in that case the question may not be pointless? ^^;; I started to read but I never saw "ExGraphics" mode so ... How would I have guessed that? Is it the extra name table attribute? And there is no mention that the scanline counter is better: am I supposed to guess that too? Only people experience with it will be able to give that information, I think.

Now I know you can access completely the rom but it wasn't obvious from checking the modes. Since they didn't say any limitation like mmc3 then I thought maybe there was a register but didn't realize it yet.

The thread was mostly since I like to chat about things that pick my interest (isn't what a bbs is all about?) and since when does we don't like to talk about things on nesdev? Did the forum change suddenly overnight? :lol: If you don't want to answer then I'm ok with that too! Thanks for the extra details, now I want to read more to understand what is different with the scanline counter.

Anyway, my point is, if there was a highlights of the main features on the wiki, I would love that since with a wall of text that is very technical, sometime it hard to get all of them in one shot.


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 Post subject: Re: mmc3 vs mmc5
PostPosted: Sun Dec 09, 2018 9:42 am 
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OK you convincted me that the thread is not as pointless as I first tought.

The wiki pages, as well as indivicual mappers docs external to the wiki are here to document a mapper. They're not here to compare mappers against eachother, that's our job. For the scanline counter, you probably know the MMC3 has a lot of restrictions : Minimum waiting time is 2 scanlines, you should be carefull about your $2006 usage as it clashes with the counter, sprites using the same pattern table as the BG will screw the counter up, etc, etc... There's none of that restrictions with the MMC5, which has it's internal scanline counter and can trigger IRQ whenever it likes.


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 Post subject: Re: mmc3 vs mmc5
PostPosted: Sun Dec 09, 2018 12:06 pm 
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Banshaku wrote:
if there was a highlights of the main features on the wiki, I would love that since with a wall of text that is very technical, sometime it hard to get all of them in one shot.
How can we improve the "overview" section ( https://wiki.nesdev.com/w/index.php/MMC5#Overview ) to make that clearer?


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 Post subject: Re: mmc3 vs mmc5
PostPosted: Sun Dec 09, 2018 1:02 pm 
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the EX Attribute thing is what i use the MOST often for megaman odyssey. i have it applied to about 95% of everything, all non-gameplay screens, levels and so on. Being able to put graphics on the screen from literally anywhere you want is a huge major advantage compared to the plain normal 256 tiles you get with the regular NES limit.

For ex att's it's technically 16000 something...but i just say unlimited cause...of course your not going to have that much in a level, the levels so far on my game have an average of 700+ "unique" graphic tiles at a time on the screen. or total for the level.


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 Post subject: Re: mmc3 vs mmc5
PostPosted: Sun Dec 09, 2018 1:21 pm 
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It's worth pointing out that BriPro's writeup about Grand Theftendo had him running into the 16k tile limit.


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 Post subject: Re: mmc3 vs mmc5
PostPosted: Sun Dec 09, 2018 9:10 pm 
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@Bregalad

That is good to know ;) I know about the bg clash with 16x8 sprites but for the 2006 case, I don't remember that. For the waiting 2 scanlines, I didn't have this issue up to now since my event were always middle+ screen so I will be careful for now. I will check the wiki again regarding the mm3 issue.

@lidnariq

Like Bregalad mentioned, I should read in more detail the page (I 'm starting to have a basic idea for now) and then I will be more than happy to give my opinion on what could be interesting for an introduction of the mapper. Ben's thread is so active these days that it got my interest and became trigger happy regarding topics. Sorry about that ^^;; Still, I'm already learning some interesting thing from it so I'm glad I started it. I may use it someday so I'm starting to investigate on the subject.

@kuja killer

Ohhh, a Mega man project, I need to check it ;) I think the Ex Attribute is what got me interested to look more into it at first. One thing I'm testing is more than 255 tiles for BG in 1 case but I could just bankswitch middle scanline to bypass that issue on the mmc3 hopefully. I need to check how it work (my guess 2 bytes per tiles? will check wiki).

I think instead of doing a comparison thread, what I should have asked is more like "who worked on MMC5 project and why did you decide to use that mapper? Which functionality did you use?". I always like to hear people opinion on their projects and what they did achieve with it.


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 Post subject: Re: mmc3 vs mmc5
PostPosted: Mon Dec 10, 2018 3:19 am 
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I know that one Konami game used the vertical splitscreen, but did any commercial games use the multiplier for anything? I'm curious as to how fast it would be.


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 Post subject: Re: mmc3 vs mmc5
PostPosted: Mon Dec 10, 2018 3:39 am 
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Sogona wrote:
I know that one Konami game used the vertical splitscreen, but did any commercial games use the multiplier for anything? I'm curious as to how fast it would be.

Uchuu Keibitai SDF is not a Konami game but a HAL-Laboratory game. Just Breed uses the multiplier in a lot of places, including the sound driver - so failing to emulate the MMC5 multiplier will fail to play back music from a Just Breed .nsf rip.


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 Post subject: Re: mmc3 vs mmc5
PostPosted: Mon Dec 10, 2018 8:38 am 
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Bregalad wrote:
Sogona wrote:
Uchuu Keibitai SDF is not a Konami game but a HAL-Laboratory game.
Oh, I was getting that confused with Laser Invasion then


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 Post subject: Re: mmc3 vs mmc5
PostPosted: Tue Dec 11, 2018 1:46 am 
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I finished to read the wiki but I still need to read more to get a better grabs of it. I understand the basic but unless mistaken, there doesn't seems to be any information for dev on how to use the extended mode for attributes and tiles. Maybe that information was in an external file?


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 Post subject: Re: mmc3 vs mmc5
PostPosted: Tue Dec 11, 2018 2:08 am 
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You're right that it's not there and should be.

For now, the important part is: the MMC5's internal nametable ("extended"), if enabled, selects a 4 KiB bank for each tile from both NES nametables. Additionally, the specific palette for the tile is the uppermost two bits.

As an example:
If CIRAM at $000 (page 0) contains 0x45
and CIRAM at $400 (page 1) contains 0x67
and the extended nametable at $000 contains 0x89, then:
if page 0 is displayed with extended attributes, the specific tile number will be 0x0945, and it will be in palette 2.
If page 1 is displayed with extended attributes, the specific tile number will be 0x0967, and it will be in palette 2.


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 Post subject: Re: mmc3 vs mmc5
PostPosted: Tue Dec 11, 2018 2:12 am 
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lidnariq wrote:
You're right that it's not there and should be.

For now, the important part is: the MMC5's internal nametable ("extended"), if enabled, selects a 4 KiB bank for each tile from both NES nametables. Additionally, the specific palette for the tile is the uppermost two bits.

Rather than "bank", I'd like to see it as the MSB of the tile #, allowing to index tiles using 14 bits instead of the usual 8. The 8 LSBs comes from the nametables as usual and the upper 6 bits as well as two-bit palette index comes from the ExRAM (shared between all nametables).


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 Post subject: Re: mmc3 vs mmc5
PostPosted: Tue Dec 11, 2018 8:33 pm 
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@lidnariq

I see. Which document should I read if I want to know more on the subject? For now, the extra tiles/color is what interest me the most.

As for testing it, I do have a dev-cart that I prepared from a KOEI cart but didn't use it yet. At the time, flash carts were almost non existent so I almost built 1 cart per mapper in the hope to use "someday" (if they are still working, who knows ^^;;).

But if someone in the future wants to test it, I guess the most common solution is with a flashcart since there is no reproduction of this mapper as I'm aware of, right? And we are still finding new things so I guess it won't be for a while either.


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