openMSX
Effect of setting bit 0 in R#0 of V99x8 not emulated
I was setting bit0 of R#0 as unwanted side effect of some optimizations on msx2 and msxTR in openmsx 20 rc1. My game was working fine on opemmsx but it was blanking the screen on real msx2 and TR.
On real hw that bit (b0 in R0) should allow superimposing to an external video signal (on tms9918 at least the EV bit has that use). The effect is that the vdp doesn't have a reference clock when there is no external signal and the screen goes blank. Real v9938/58 seem to show the same behavior of the tms9918. On v9938/58 manuals that bit is undocumented.
BlueMSX instead seems to have implemented that bit correctly
Openmsx on msx2 doesn't implement that bit
We can't find anything that blueMSX does with that bit. It does do something with bit 6 (DG - Digitize).
