Alex Wulms should know about the VDP command engine... as he wrote it 
I confirm that the VDP command engine in the OCM is faster then in the real MSX. Getting the timing exactly the same is difficult. Ideally, I would need to measure at bus level how the real VDP behaves so that I can build a better model for the state machine but for that I would need to connect a digital scope to my real MSX. Unfortunately I don't have a digital scope so this path to further analyze the timing is not possible for me.
Though, an alternative is to read status register 8 during command execution (it contains the tmpSX value used to keep track of the source-x coordinate during copy commands). By analyzing how this one changes (with screen on or off, with sprites on or off, etc) it should be possible to build a better timing model and improve the OCM accordingly.
It is still on my to-do list to make the test programs and analyze the results.
Kind regards,
Alex
SystemTimer(TurboR compatible I/O port E6h, E7h) is installed in EMSX_TOP_20080502_002.ZIP.
I made the bench mark of HMMM by using it.
HMMM(Sprite ON) of OCM was about genuine twice velocity.
It is difficult to match it completely.
However, it is possible to bring it close a little more
I will add a high-speed mode and the real mode to VDP.
I've tested this version and XAK freezes during the intro
I did not know the problem.
Certainly, Xak is freezed according to the timing of lightning 
I will investigate it.
