Emulation for develping SW that works on real HW: FEATURE REQUEST

It should be possible with an openMSX TCL script. Mayhaps somebody with a bit of knowledge there can make you one.

I think I would be able to make a script that checks if the time between two writes on I/O port 0x98 is smaller than a certain value and put the result in the console or a file. Would that help?
If so, I'll make an attempt to write such a script. You can help by precalculating the time

I'm going to make a small script, not going to change the debugger GUI. Consider it a proof of concept. 26 cycles is nice, but I need it in (micro)seconds

When such an out occurs, I could simply print the current PC.

If you give me a sample program with some known 'bad outs', I can use it to test the implementation.
Please join #openMSX to continue this discussion more easily (e.g. via http://openmsx.sf.net/mibbit.php )

This very simple script should get you started, you can tweak it till it matches exactly your needs. To use it, save it to some file e.g. vdp-timing.tcl and then in the openMSX console type

source vdp-timing.tcl

set last_vdp_time 0

proc vdp_io_write {} {
        global last_vdp_time
        set now [machine_info time]
        set min_diff [expr 26.0 / 3579545]
        if {($now - $last_vdp_time) < $min_diff} {
                # tweak this line to generate the logging you like
                puts stderr "Too fast VDP access detected (pc = [reg pc])"
                # uncomment this line if you want to break at this point
                # debug break
        }
        set last_vdp_time $now
}

debug set_watchpoint write_io 0x98 true vdp_io_write

Manuel is still working on a more extended script. For example to ignore timing problems when screen is disabled, or to only log an error once for the same instruction.

manuel, your script ROCKS!!!
I haven't jet tested the new DDA code after the patches, but without your script it would have been a pain find all the criticalities !
THANKS!!