2018-12-10 19:48:06 +11:00
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# Work RAM
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2018-12-17 16:01:23 +11:00
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## External Work RAM (EWRAM)
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* **Address Span:** `0x2000000` to `0x203FFFF` (256k)
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This is a big pile of space, the use of which is up to each game. However, the
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external work ram has only a 16-bit bus (if you read/write a 32-bit value it
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silently breaks it up into two 16-bit operations) and also 2 wait cycles (extra
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CPU cycles that you have to expend _per 16-bit bus use_).
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It's most helpful to think of EWRAM as slower, distant memory, similar to the
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"heap" in a normal application. You can take the time to go store something
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within EWRAM, or to load it out of EWRAM, but if you've got several operations
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to do in a row and you're worried about time you should pull that value into
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local memory, work on your local copy, and then push it back out to EWRAM.
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## Internal Work RAM (IWRAM)
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* **Address Span:** `0x3000000` to `0x3007FFF` (32k)
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This is a smaller pile of space, but it has a 32-bit bus and no wait.
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By default, `0x3007F00` to `0x3007FFF` is reserved for interrupt and BIOS use.
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The rest of it is mostly up to you. The user's stack space starts at `0x3007F00`
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and proceeds _down_ from there. For best results you should probably start at
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`0x3000000` and then go upwards. Under normal use it's unlikely that the two
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memory regions will crash into each other.
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