Is there such a thing as an MZ demoscene?
Excellent. Thanks for that explanation, very detailed. I remember you mentioning it before in regards to making changes to the display on the horizontal blanking period etc I hope to try this out properly on my MZ-80A soon.
Also, the snow effects on MZ-80 K is merely due the fact that Z80 is reading/writing in VRAM while video circuit is reading bytes from VRAM precisely because there is no setting /WAIT to 0 when drawing during horizontal rasterline.
The /WAIT facility is for any device which needs to supply it and it is a common Z80 signal: for instance, when you plug you own PCB in the expansion bus (/EXWAIT signal) and want to make the CPU able to adjust to slow chips (/EXWAIT signal is connected to Z80 /WAIT signal). MZ-80 K has no LSI to handle mutual storage access exclusion. MZ-80 A is a mistery for now (I hope @psmart can tell me more about it).