[MiNT] memory protection on Afterburner040

[joy@sophics.zln.cz (Petr Stehlik)]

Hi,

thanks to Gryf and other FreeMiNT programmers I finally could see the
MiNT running with memory protection. My usual KGMD setup booted OK
(after disabling ST-Guide). Later it killed ZCONTROL and JCLKTOOL (I
kinda liked that - a nice alert instead of TOS bombs, even if I didn't
know these two ACCs should have been ill).

Then I tried to play with some 'dirty' programs like a HexEdit (direct
memory editor). I was quite surprised I could edit memory at 0x8xx
without any alert - why? The memory allocated before MiNT has started is
not write protected? Probably not. This is still a weak place. But
protecting such memory would require MiNT to learn where the screen
memory is and where the cookies are etc. Probably too complicated?
Is memory protection tied with User/Supervisor mode anyhow? Would it be
possible to protect such low memory addresses in user mode only?

Later I started GemBench because the system seemed to be slower than
usually. All but RAM/ROM tests went fine and showed that the memory
protection slows down just VDI inquiry and FPU (50% of usual speed). The
rest was OK. Though the RAM/ROM tests cause system freeze - why? No
alert, no program is killed, it just stops the whole system. Anybody
experienced similar behavior?

Petr
--
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