Wilf Rigter has written programs, which use hires display in the upper screen area and text mode in the lower area.
So everything is possible, when using a ZX81, but somebody needs to do it
But be careful: works only on real original Zeddies (not on machines, using a non-compatible ROM like ZxPand, Mefisdos, ZxNU, ZxMore, ZxBlast, ZxDeluxe, ...)
As I have already written in the other thread: bend the ram's pin /OE up and connect it to the Z80 /RD signal (e. g. at the edge connector).
That solves the timing problem during WRITE cycles ....
I've compared the Hitachi chip against the half K chip read cycles and it looks like /OE is doing nothing. Looks like the whole thing is driven by the /CE and I should instead tie /OE to ground? Or do I have that wrong? This diagram shows a "Read Cycle (1) (/CE controlled )" Maybe it has also a dif...