I've started writing an assembly debugger that uses a branch instruction as a breakpoint. Currently the debugger and debugee (?) are modified with a different pair of branch instructions for each debugee instruction that gets single stepped. So far I just have a limited proof of concept and, the few times I've loaded an external program as the debugee, I've just been lucky that it's been in the 16MB range of the branch instruction.

I know that either the LR or CTR could be used to branch anywhere in memory but the debugee may want to use those registers and working around that seemed like it would get messy. Moreso...

To be honest, when I came up with this approach, I'd lost sight of the fact that modern systems have so much more memory than classic Amigas. But I figure that a debugger that's limited to working with programs that fit into 16MB is better than nothing.