alt Hacker NewsForty years ago I had a Sinclair QL with an 8086 emulator. Because the Sinclair QL had preemptive multitasking, I could easily search memory for patterns, monitor locations, stop and start the emulation, or change memory programmatically and easily from the QDOS side. It was worlds easier than using a debugger, particularly since I didn't own an 8086 system.
I always thought it was a clever way to get insights in to software while it was running that wasn't available to people with 8086 systems, and it's interesting to see this idea so many years later.
Bochs and MAME both have superb and widely-used debuggers, while Qemu is more limited but still has some debugging capabilities in its monitor, as well as a gdb integration. (Can’t say anything about PCem/86Box.) It seems that developers of emulators targeting good coverage of old stuff simply can’t not build a debugger, because it’s an integral part of their task to figure out what the hell the devs of the latest failing thing did to make it fail. Bochs is (was?) also quite popular in the OSDev scene as a debugging tool.