[MiNT] Memory protection difficulties

[Mario Becroft <mb@tos.pl.net>]

No doubt you will remember my recent messages on this list about
attempting to utilise memory protection on my TT. It failed to begin with,
but after setting the program vconsd to global memory everything worked
reasonably well.

It is certainly very good having memory protection, and I avoided a couple
of potentially nasty crashes while developing some software because memory
protection was enabled. However I observed the following problems while
memory protection was enabled, which have led me to disable it once more.

I do not claim to have perfect knowledge of every thing about the issues,
and some of the things are obviously not a fault of MiNT. Nevertheless as
they affect how MiNT can be used I think they are still relevant.

Firstly the machine operates noticable slower with memory protection
enabled. Particularly shell scripts seem to take much longer to run,
logging in takes several times longer than it does with memory protection
disabled, and other operations are also slower. However other things seem
to be unaffected by this slowness.

The other problems relate primarily to GEM and certain programs in
particular. ST-Guide completely fails to operate which is a severe problem
since I use that program very frequently. Also I can no longer quit from
N.AES because upon doing so, the computer freezes. Also I can't find any
control panel program that works well - Z-Control causes a memory
violation when closing a CPX, Freedom I got rid of some months ago and I
have never looked back because of much less crashes, and COPS requires
WDIALOG which causes the machine to crash rather frequently. Or should I
go back to XCONTROL despite its limitations?

Lastly, and possibly the worst problem since it is unpradictable, is that
since enabling memory protection, I get occasional (about once every day
or two) inexplicable crashes where the computer just freezes. It can
happen at any time, whether the computer is being used at the time or not,
and when it happens the machine entirely does not respond, although
pressing the reset button reboots the machine and everything is back to
normal. But this amount of crashing is unacceptable and in the end is the
main reason why I have disabled memory protection.

I am sure I cannot be the only one who uses memory protection and has
observed some of the above problems. I would be very interested to hear
any comments on the above.

-- 
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| Mario Becroft                * Tariland, New Zealand Atari User Group |
| mb@tos.pl.net                * Atari Hardware Developments            |
| http://www.ak.planet.gen.nz/~mario/ * Atari Serial Mouse Interface    |
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