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Old 24 September 2013, 02:05   #432
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Originally Posted by commodorejohn View Post
Uh, no. No no no. Tilemaps are arrays of pointers to actual tile definitions that have to be stored in graphics memory. Tiles themselves take up just as much space as Amiga graphics of equivalent resolution and bitdepth, because they're just small bitmaps. If you're using 16-color 8x8 tiles, you can store a maximum of 2048 tiles in 64KB. (And as for word-length tilemap definitions, not all the bits are used for the pointer - there's also palette select and horizontal/vertical flip bits.) There's also the fact that the tilemap itself has to go in video memory, along with the sprite parameter list. (Can't remember whether the palette definitions do, though.) Tilemap hardware isn't magic.

And doing tiled graphics on the Amiga would take up the exact same amount of space for the graphics at equivalent size and bitdepth, plus a screen bitmap for the output (and the code itself would take up some memory and CPU time.) Not "megabytes."
The tilemap system never have direct access to the tiles. The main processor is requesting the tiles display by the X/Y hexa coordinates in VRAM. This is why you can make graphic operations that an amiga just won't be able to do.

Look at Megadrive, CPS-1, CPS-2 games. The 68000 take care of the game logic, and is constantly pushing tiles coordinates (bytes or words) to the graphic chips, and the same happens for the sprites.

The tiles in themselves are stored in ROM, they take their weight as you said, but it was not my point.

the amiga is moving the tiles in RAM "really", when a console or a coin-op machine is only moving tile references in VRAM. CPS system and megadrive are helped by a much flexible and powerful hardware functions.

Tilemap system are not magic, they just remove a huge burden off the back of the main processor. And should i add that the CPS-1 for instance has the ability for example to perform hardware calculation (yes, capcom hardware engineers have actually moved this function inside the PPU chip.), this means that the board can process calculations that would make the 68000 sink if it had to do it itself.
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