4 ms·

I'm guessing the problem occurred specifically with CPUs newer than the 68000 irrespective of amount of RAM? (Microsoft's) Amiga Basic also did this and stoppe

by vidarh 3y ago

I'm guessing the problem occurred specifically with CPUs newer than the 68000 irrespective of amount of RAM? (Microsoft's) Amiga Basic also did this and stopped working on newer CPUs, as the 68000 only has 24 address lines and ignores the top 8 bits of a 32 bit address, but 68020 and up uses all 32 (I don't remember about the 68010, but that was pin compatible with the 68000 so I'm guessing not)

ithkuil 3y ago
The 68010 was indeed pin compatible with the 6800 and had only 24 address bits. But the 68012 (which was otherwise software compatible with the 68010) extended the address bus (and had more pins) and was the first m68k CPU to exhibit this compat issue. The 68020 was more popular but came a couple of years later
- vidarh 3y ago
  That's interesting. I'm not sure I was ever aware of the 68012.
  - ithkuil 3y ago
    Possibly only used by Alliant
KMag 3y ago
There was hardware (not sure if it was CPU state or state in the memory controller) to zero-out all of the address bits above the 24th, allowing backward compatibility. I forget the shortcut (option-I? option-M?), but if you selected an executable in Finder, you could go in and change the hardware compatibility mode used to run it.
- vidarh 3y ago
  That's interesting. I don't think the address hack was widely used on the Amiga, so we didn't get anything like that. Amiga Basic was the main one and that was ditched for Arexx for the newer OS versions (a shame, because as much as I liked to mock Microsoft at the time, Amiga Basic was quite decent). I don't think the incompatibility had anything to do with ditching it - people have patched it and it wasn't a big deal; I'm assuming it didn't get an official patch because Commodore had already decided to replace it.