In mga_drm.h comments indicate that only DSTORG and TEXORG is validated.
I think bit 15 (memreset) of MACCESS should be checked as
"The memreset field must always be set to '0' except under specific conditions
which occur during the reset sequence."
Seems like something which should not be accessible to normal users.
ajax at nwnk dot net,
Do you still experience this issue with newer soft?
Please check the status of your issue.