The Super Nintendo’s graphics chip could turn and scale one flat background picture. Nintendo’s developer manual: “Mode-7 is a screen, which can rotate, enlarge or reduce.” Nintendo calls it the ability “to take hefty 2D shapes and twist and spin them through three dimensions”, “allowing games like Super Mario Kart to create pseudo-3D tracks.”
The trick behind a road that runs to the horizon: the screen is drawn line by line, and every line can get its own zoom. The manual describes H-DMA, a form of DMA (direct memory access), as “a special DMA which can transfer data automatically, synchronizing with the H-Blank”, the short pause after every line, and says “The S-PPU settings can be varied by each horizontal scan line.” DMA moves data “by using the hardware instead of the CPU”. The picture has 224 lines (“256-dot x 224-dot”; the sky part needs no zoom). The processor only prepares the list, H-DMA delivers one entry per line.
Book I of the manual never mentions roads. The link follows from two passages: the zoom values sit in graphics chip registers, and H-DMA writes those registers line by line. The SNESdev Wiki says the transform “can be changed every scanline via HDMA”. The processor still pauses briefly during each transfer; it just runs no code for it.
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Sources: Nintendo, SNES Development Manual, Book I (chapters on Mode 7 and DMA/H-DMA); Nintendo UK, “Super Nintendo” (Nintendo History, “Graphics Power”); Nintendo UK, “Nintendo Classic Mini: SNES developer interview, Volume 2: F-ZERO” (20 Sept 2017); SNESdev Wiki, “Mode 7 transform” (community documentation).
The background, the King, the racing track, the kart, the console, the TV, the DMA chip and all other pictures are our own illustrations, not real products, people or game screens.
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