CompuServe Messages

Actually, a lot of that low memory is "reserved" by the 68000 itself rather than the Amiga. The vectors for traps and interrupts are stored in the low 1K of memory because that's where the 68000 wants to see them. I believe the 010 and 020 are more flexible about where those tables can be put, but with the 68000 there's no choice. So, although 4 is the only fixed location as far as the Amiga OS is concerned, that whole stretch of memory is also fixed by the CPU. Many programs do accidentally write more or less benignly into that space. The 3.4a Aztec assembler frequently writes a $62 to location 12; since that's the high byte of a pointer it does no damage (at least with a 68000). The first release of Professional Page writes twelve successive bytes of garbage starting at $30 or so, but that's a reserved, unused slot in the vector table so it gets away with it. It would be nice if developers would check to make sure that their programs don't write to low mem before releasing a product, though; even when those writes don't crash the machine, they do point to something unintended happening in the program, and of course may be disastrous on some future Amiga where things are arranged a bit differently. Nick