Hi all,
Ooohh, it's really hard to explain those Brazilians all about memory
mappers! (don't they have any?).
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.
Apparantly there exist Philips MSX-2's without a mapper (not the
8220, which has a mapper), because I made a schematic once for
building 128K mapper in those (if all Philips MSX-2's had mappers, I
wouldn't have). I suppose the VG 8230 could be such a machine. If you
have a VG8230: check it! Does this one have a mapper, or not? Be sure
it is a 8230: I've helped build a 8235 into a 8230's casing once...
128K mappers in <>Philips machines:
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.
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?
Bigger:
Turbo-R: 256K (ST) or 512K (GT), mapper
Sony HB-G900AP (note the "A" in there!): 512K or 1 MB., mapper
Greetings,
Alwin Henseler ([EMAIL PROTECTED])
http://huizen.dds.nl/~alwinh/msx MSX Tech Doc page
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