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EnigmA Amiga Run 1996 February
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EnigmA AMIGA RUN 04 (1996)(G.R. Edizioni)(IT)[!][issue 1996-02][Skylink CD III].iso
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MONi-HardProblems
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1995-05-08
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Hardware problems...
We are working on a software/hardware project for the amiga computer, the
hardware is expected to support 68020,68030,68040 and newer updates available
on amiga.
Our system is based on the idea that it should be possible to freeze a
program and enter into our monitor, preferably totally invisible to the
system.
Currently the software runs with a simple Level7 hardware interrupt by altering
the level7 vector.
Our problem is that 68020+ can change the address of it's exeption vector
assignments $0-$400 (VBR).
We are looking for a way to generate a Level7 interrupt that will work
even if the VBR has been moved. and without using OS routines in any way to
get hold of the VBR address.
We have been trying some different theories...
Co-Processor emulation... since the coprocessor has access to all the internal
CPU registers, the problem is that the instruction run has to be an Fline..
opcode $f000.
It would be a lot easier if the cpu space was accessible by some simple bus
operations.
We also considered intercepting the cpu bus cycles when a level7 is generated
and then switch the memory off and supply the bus with our exeption address.
As you can see we are open to any suggestion if it is at all possible to get
hold of the VBR and by some way change it in our favour.
(sorry about the rather chaotic phrasing used...)
Nicholas Clarke
Contact me if you can help!