Re: [openMSX-devel] Mapper

[Wouter V. <wou...@st...>]

On Tue, 15 Jan 2002, Alex Wulms wrote:

> ] Masking only works if the mapper has a power of 2 number of 16kb blocks.
> ] I think this is a reasonable restriction, but then we should also check
> ] the input from the config file.
> ] ...Is it theoretically possible to have non power of 2 sized mappers?
> Yes. Certainly in theory.
>
> And also in practice. E.g. Mapper of turboR is non-power of 2 when operating
> in RAM mode; the 4 highest ram pages are not visible anymore in the mapper...

What exactly is "not visible anymore"? If I do select one of the last 4
pages, what happens if I read from it or write to it?

Which ROMS are replaced in RAM mode
 - BIOS ROM
 - BASIC ROM
 - SUB ROM
 - ...
Which is the 4th ROM? I vaguely remember it was somethimg with KANJI.

How do we model this in openMSX? The ROM and main RAM in Turbo-R are
strongly coupled. Does this mean they must be modeled as a single
MSXDevice?
Or maybe we can directly alter the slot-structure: unregister the ROMS
and register the mapper instead.


Wouter