RE: floppy disk change (was Re: 1.15 kernel)

[Konrad Kokoszkiewicz <draco@mi.com.pl>]

> I agree with Konrad, current TOS handling of floppy disk-change is
> primitive and wasteful. Unfortunately, without a genuine media-change
> hardware signal (and corresponding interrupt) there's not a lot that
> can be done to improve the situation. I also agree that floppy disk
> access is already slow, and slowing it down further should be avoided
> if possible. Currently TOS uses a VBL routine to poll the write-protect
> status of the drives. It's inefficient, but it really ought to be good
> enough to detect that a diskette was removed/inserted. In the default
> case, where the write-protect status has not changed, I don't believe
> it's necessary to re-read the boot block. Explicitly reading at every
> directory operation would totally negate any effort to cache FAT info.

Hm, not exactly. You'd need to invalidate cached FAT info only if you
realize a disk change took place. I agree that may be tricky, but I really
think that trying to re-read the bootblock at each open() operation would
be better (though eventually slower) that guessing the media change from
the heaven's state. It usually takes me more time to convince the TOS that
I changed the floppy, than it probably would take if the system would be
re-reading bootblock at each open(). 

Anyways, whatever way, something has to be done with this. Possibly, what
about mount/unmount floppy mechanism for MiNT? That would eliminate the
confusions, because the user would just have a possibility to explicitly
tell the system that the floppy was changed... Julians FORCEMED.APP
usually does the trick when I am in GEM (on Falcon), but I have one
computer at work, and no monitor for it, so I have to access it via
telnet. FORCEMED.APP doesn't fit well in such an odd setup :-)

> > > Number of free clusters? In sector 0?
> >
> > Yeps. Where you'd exspect number of free clusters?

Now I have to correct myself: the TOS filesystem doesn't keep the number
of free clusters in the sector 0. I've just messed up two different
filesystems. 

--
Konrad M.Kokoszkiewicz
|mail: draco@mi.com.pl                  | Atari Falcon030/TT030/65XE |
|http://www.orient.uw.edu.pl/~conradus/ | ** FreeMiNT development ** |

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