DOS-2 and mapper weird behaviour

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Par Grauw

Ascended (10772)

Portrait de Grauw

02-01-2023, 23:34

aoineko wrote:

So, I don't understand why the documentation about MSX-DOS 2 asks to detect the presence of the extended BIOS before using the Memory Mapper handling routines. If there is no case where extended BIOS is not present under MSX-DOS 2 why bother to detect it?
For ex. :

The mapper support routines are an independent API and they can be used without MSX-DOS2, e.g. through the use of MU.COM. If your program has other dependencies on MSX-DOS2 as well and already checks for that, then indeed the Extended BIOS detection is a bit superfluous (though I do it anyway).

Quote section 5.2:


A program can use the extended BIOS calls for the mapper support to obtain these addresses. The calls are provided because these addresses may be changed in the future version, or to use mapper routines other than MSX-DOS mapper support routines.

To use the extended BIOS, the program should test "HOKVLD" flag at FB20h in page-3. If bit-0 (LSB) is 0, there is no extended BIOS nor the mapper support. Otherwise, "EXTBIO" entry (see below) has been set up and it can be called with various parameters. Note that this test is unnecessary for the applications which are based on MSX-DOS (such as the program which is loaded from the disk), and the program may proceed to the next step.

Par aoineko

Paladin (1004)

Portrait de aoineko

03-01-2023, 01:43

Ok, it's clear now. Thanks.

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