Hi Eric,
First of all thanks for responding!

That solves a part of the problem, the connection of the external ram-ic and the 8052 but the other part remains: The µC needs to control the ram-ic to send out the screendata to the 8 shift-registers (refresh) spending lots of time doing so and I think the problem then is that refresh-rate will be quite unstable according to what a program has to do between 2 refreshes.

I did a little thinking and sketching on paper. What if I had hardware(let's call it VCU:Video ControlUnit :-) ) handling the refresh with the 74595ic's with a steady refreshrate, and have it send an interrupt to the 8052 when a refresh is done to let it know an update of video-ram is allowed for x millisecs. The µC should intercept the interrupt of the VCU and decide if video-ram is to be updated or not.
This way no refresh-variantions or so are seen on the display, and it could work perfectly, but it sure makes the program more complicated :-)
Is this a good solution or do you think better ways exist?

thanks again
Jeffrey