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Hope not to be in the wrong section. I choose this since the description talk about tools...

When choosing my emulator (yes, you right! Use both would be better) between qemu and bocs i choose bochs because of its native debugger. It was, anyway, an in-reserve-choice since gdb was not stopping on the instruction where i set the breakpints but a bit later.

I recognized that by placing a simple print (probably, MMIO would be better instead of interrupt) at 0000:7c00. It first print the character and then stops.

Do you also have such a problem or it just my own?

I apologize to haven't been clear.

I started using Qemu but it was giving me this issue, so i switched to bochs to have native debugger. Currently, i'm using bochs but i really want to use qemu. To do that, i need to have gdb debugging properly but it has this misbehaviour that makes debugging impossible (a "delay" of one instruction is already to much).

I am able to recognize this misbehaviour also in onother way: place a breakpoint to 0000:7c00. When gdb stops qemu says (in its dedicated console) to be ahead (i.e. in 0000:7c01, supposing a "cli" instruction at 7c00).

Hope to have clarified something