At 02:40 PM 3/15/99 -0300, you wrote:
>> And ROM pages are 8K in size, mapper pages 16K. This means that sometimes
>> you need to duplicate ROM pages in the mapper to allow all combinations
>> used by the game. Example: ROM page 0 and 4 are used together, just as ROM
>> page 0 and 13. In the mapper you'll need 2 pages (32K) for those three 8K
>> pages (24K).
>
>If you have 256kb of RAM, there's enough space to do all the necessary
>combinations. Or am I wrong?
It depends on the game. In theory, it could use 16 * 16 = 256 combinations
of two pages. That would require 4MB RAM. But in practice, only a very
small amount of combinations is actually used. 256K should be enough to
contain all combinations in 95% of 128K ROMs.
>> Many MSX2 games use only 64K VRAM. Firebird and King's Valley 2 are >>
examples.
>
>Ok, but VRAM needs to be copied to RAM. If you need to copy data, you can
>transfer RAM to RAM and make the necessary block combinations with LDIR.
Yes, RAM to RAM copy is preferable, _if_ you have enough RAM available.
>I have never seen a MSX2 with less than 128kb of VRAM.
Neither have I.
But for example Hydlide 1 checks for 64K or 128K VRAM and displays a
different loading picture for both cases.
Bye,
Maarten
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