Hello!
Since it's an external chip that generate the bus error (acces fault in the 68 0 [46]0 terminology), we cannot skip it with the PMMU. Even if we say in the PMMU tree that this zone is user-readable, any attempt to do so will still generate an exception.
Sure, but for programs this area shouldn't be mapped anyways (at least only supervisorprotected or alternativly not to the physical memory).
So we can only affect memory protection on 0x0000-0x2000 at once. But 0x0800- 0x2000 is user readable/writable on standard Atari, so programs are allowed to access it in user mode. This would generate a bus error under MiNT MP if we protect the whole memory page. This is a problem since there are some interresting datas there (Line-A variables among others, IIRC), that a program may legally try to access in user mode.
I didn't see a problem here. Even Line-A should be supervisorprotected (on Milan this is so done for example).
PS: I guess I was too verbose, but I wasn't sure how I should uderstand your question. So I decided to explain the whole thing. I hope you will find your answer inside all this noise...
No problem, better a verbose answer than a to quiet answer :-) Regards, Frank -- ATARI FALCON 060 // MILAN 060 ----------------------------------------- http://www.cs.uni-magdeburg.de/~fnaumann/ e-Mail: fnaumann@freemint.de