DK JR Math repro issue

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Pokun
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Re: DK JR Math repro issue

Post by Pokun » Tue Mar 23, 2021 12:04 pm

Muramasa said himself somewhere on this board that he used the official H and V indicators. H and V indeed means horizontal and vertical, but it refers to the nametable arrangement, as several people said, not the nametable mirroring like the iNES header and the wiki do. Arrangement is the exact opposite of mirroring.

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tokumaru
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Re: DK JR Math repro issue

Post by tokumaru » Tue Mar 23, 2021 7:17 pm

Like Pokun said, "H" always means "horizontal" and "V" always means "vertical", the confusion revolves around what these words are describing. The NES has a virtual scroll area of 2x2 screens, but only has the memory for 2 actual screens, so 2 of them are unique and the remaining 2 are copies, or mirrors, of the other 2.

Original Nintendo boards use these words to describe how the 2 unique screens are arranged in the 2x2 space - a "horizontal" layout means that the unique screens are placed side by side, and those 2 screens are vertically mirrored, while a "vertical" layout means the screens are stacked on top of each other, and horizontally mirrored.

For some reason, during the dawn of emulation, one of the first NES emulator authors chose to disregard the convention used in original cartridge PCBs and describe the mirroring of the name tables instead of their layout. And this confusion still causes problems to this very day, as you experienced first hand.

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