I thought I'd have a quick look at the
new Repton3 loader to figure out why it won't load from ADFS / NFS. Got myself really confused when using the *REX disassembly tool that is part of the Advanced ROM Manager (ARM) Utility ROM. Initially testing on real hardware, this is what I was being presented with when issuing a *REX0 A9C command:
- *REX0 A9C output
Addresses &AA2 thru &AB2 didn't make much sense. I thought the code was self modifying because if I changed address &AA2 to RTS, it would change back again. But I couldn't figure out what was modifying the code. Hmmm.
So I moved over to BeebEm to see if the debugger could shed any light on the matter, and I got different results! Now, that looks more sensible:
- BeebEm debugger output
Why the difference??? So I run *REX0 A9C from within BeebEm, and I see the same as I see on the real hardware. Check the debugger, and it's changed as well!
- BeebEm debugger output after *REX0 A9C
I can only assume *REX is using Page 10 for its own workspace, and is therefore corrupting the code that I'm trying to debug
. I've wasted a couple of hours on that
. And now that I think about it, I'm pretty sure I've seen this problem before.
