Ok I've worked out what is happening. Dosbox is only matching breakpoints based on seg and offset not on the actual address. I made a small change to bool CBreakpoint::CheckBreakpoint(Bitu seg, Bitu off) in src/debug/debug.cpp to check break points based on their flat address and it seems to work …

Hi Guys, Just a quick question regarding the dosbox debugger. I'm new to asm programing so please bare with me if my question isn't 100% dosbox related. I'm trying to debug Ultima 6 using IDA Pro 4.3 for DOS and the internal Dosbox debugger. I seem to have a problem setting the break points in …