The leftmost tile in offset-per-tile mode

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jeffythedragonslayer
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The leftmost tile in offset-per-tile mode

Post by jeffythedragonslayer »

Does anyone know anything about when this quirk happens?
Offset-per-tile never affects the first (leftmost) tile
I do not observe this behavior in Yoshi's Island World 1-7: Touch Fuzzy Get Dizzy on my 2/1/3 console. All the tiles in the leftmost column appear to move when Yoshi is dizzy.

Source: https://snes.nesdev.org/wiki/Errata
lidnariq
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Re: The leftmost tile in offset-per-tile mode

Post by lidnariq »

The leftmost fetch comes from the normal scrolling registers. Every subsequent one is loaded from VRAM.
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jeffythedragonslayer
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Re: The leftmost tile in offset-per-tile mode

Post by jeffythedragonslayer »

lidnariq wrote: Tue Aug 30, 2022 7:20 pm The leftmost fetch comes from the normal scrolling registers. Every subsequent one is loaded from VRAM.
Yes, that is how I interpret the statement. So, it appears that this quirk was fixed in the PPU revision that I have. It will be fascinating to see what else all changed once we have the PPUs decapped. :)
lidnariq
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Re: The leftmost tile in offset-per-tile mode

Post by lidnariq »

No? The game is programmed to compensate.

To check on your hardware, you could use my "ppu bus activity" ROM and look at the left-most 1-7 pixels in the mode 2/4/6 regions. They should jump abruptly up and down relative to the right 96% of the scanline.
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rainwarrior
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Re: The leftmost tile in offset-per-tile mode

Post by rainwarrior »

This is by design, not really "errata". When horizontal scroll isn't a multiple of 8, you have 33 visible tiles, not just 32. They needed to make an extra one addressable somehow.
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