IIRC the issue was that 68000 would transparently mask the top bits, so code could get away with avoiding the explicit masking, which of course breaks when you

IIRC the issue was that 68000 would transparently mask the top bits, so code could get away with avoiding the explicit masking, which of course breaks when you move to a larger address space. More modern cpus enforce specific bit patterns for the MSBs, so broken code would be caught immediately.