On Fri, 19 Mar 1999, Alwin Henseler wrote:
> Ooohh, it's really hard to explain those Brazilians all about memory
> mappers! (don't they have any?).
Not all Brazilians (or am I being so repetitive?). I converted several
games from Memory Mapper to Megaram, and I never had Memory Mapper!
> Some facts:
>
> An MSX2 doesn't need to have a memory mapper to be a true MSX-2.
> Example: Sony HB-G900. 64K RAM, no mapper, but true MSX-2, nothing
> wrong with it.
That's what I said!
> Sony HB-F9P: 128 K, mapper
>
> Smaller:
> Almost every Japanese-built MSX2 or 2+: 64K mapper
>
> Philips NMS 8220 has only 64K, but this IS a mapper. Really a 128K
> mapper with 2nd half empty, so switching blocks, you get:
> Block 0, 1, 2, 3, "nothing", "nothing", "nothing", "nothing", block 0
> again, 1 again, 2 again, 3 again, "nothing", "nothing", "nothing",
> "nothing", 0 again, 1 again, etc.
Then, it can be expanded to 128kb.
> Not standard? Absolutely standard!
> Mapper=64K = 4 blocks (0-3), selecting block 0, 1, 2, 3 gets you
> mapper blocks 0, 1, 2, 3 -> all ok.
> Reading the mapper ports on this machine would return other
> values as you might expect, but reading mapper ports SHOULD
> be considered unreliable, right?
Not only unreliable, but a wrong procedure, since the MSX Technical
Handbook prevents it.
Greetings from Brazil!
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Marco Antonio Simon Dal Poz http://www.lsi.usp.br/~mdalpoz
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