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PostPosted: Sat Aug 20, 2005 2:01 am 
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Look at the Nametable viewer in FCEUXD with somme licenced games when they scrolls. You'll undestand by yourself.

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PostPosted: Sat Aug 20, 2005 12:55 pm 
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Alright, did it :D

What it seems to me is that the nametable itself deals with the background... and I'm guessing that vertical mirroring is called so because the background tiles(?) generate vertically from top to bottom. I haven't tested any horizontal yet, but I'm guessing the tiles lay out horizontally. I think the scroll line shows where the left side of the screen is.

Now, I noticed that the nametable at $2000 and $2800 (like in Membler's post on the other thread), as well as $2400 and $2C00(?) are the exact same. Why is this? I don't understand exactly what it accomplishes when it looks to me like the addresses at $2000 and $2400 are doing enough... or is there something that $2800 and $2C00 are doing that I'm not aware of that add to it?

By the way, I tested mainly with Mega Man 2 and Super Mario Bros. 2 (USA).


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PostPosted: Sat Aug 20, 2005 1:17 pm 
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Well, I don't understand why you're still asking questions so. Yeah, the vertical and horizontal mirroring means that the duplicating of the nametables themselves are done vertically or horizontally, respectively. It would seems more logical to call them on the opposite way, like on the solver pads where there is hardwired mirroring.

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PostPosted: Sat Aug 20, 2005 8:36 pm 
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Roth wrote:
Now, I noticed that the nametable at $2000 and $2800 (like in Membler's post on the other thread), as well as $2400 and $2C00(?) are the exact same. Why is this?


It's because the NES has only enough VRAM for 2 nametables, but there's enough address space for 4. They made it so you can select on the cartridge which 2 tables are usable (and which 2 tables are mirrored) by connecting a couple pins together on the cart.

It's pretty much there so you can choose between scrolling horizontally or vertically without having partially-drawn parts of the nametable on-screen.


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PostPosted: Sat Aug 20, 2005 8:41 pm 
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Alright, awesome... I pretty much get it now. Thanks for your replies!


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