Re: GEMDOS from VBL

[stehlik@cas3.zlin.vutbr.cz (Petr Stehlik)]

On Sun, 14 Jun 1998 17:04:31 +0200 (MET DST), Johan Klockars wrote:

JK>First a rather fundamental question:
JK>
JK>  Do you really need the VBL at all for Clocky under MiNT?

Clocky is a general utility that should run under all available
operating systems. There's no OS-specific code yet.

JK>> a little update of my previous message: calling Malloc(-1L) from VBL
JK>
JK>I haven't looked that much into the MiNT code, but it is by no means
JK>obvious that all parts of GEMDOS should be reentrant.

I haven't looked into MiNT code at all, though I seem to remember that
the re-entrance of GEMDOS was one of main advantages of MiNT over TOS.

JK>After all, MiNT
JK>doesn't multitask once supervisor mode is entered and the original OS
JK>code is still used for some things.

yes, that's right.

JK>As was said before, OS calls from interrupts are often a very bad idea.

But how one can write TSR then? I need to do a lot of things, and system
variables are not documented. How would you, for example, changed
current keyboard layout mapping? The system variables are undocumented,
so I need to call OS call from interrupt.

JK>> and Dfree('U') behaves very strangely, though: it returns numbers from
JK>
JK>What should that call return anyway? The same thing as Malloc(-1) or the
JK>total amount of free memory (such as you can get by looking through the
JK>allocation list)?

total amount of free memory. It goes through the allocation list and
sums the free blocks up. This is handy, though sometimes one would like
to write an utility for displaying every free memory block (e.g. for
watching memory fragmentation) and then it's impossible to write it with
MiNT (without using dirty tricks).

Making the memory allocation list somehow available for reading would be
useful, I think.

Petr
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