[Oberon] Oberon on Ultibo

[greim]

Hallo Bernhard et. al.

I m just a little busy in my job, but I will continuo wit UltibOberon as 
soon as I have a little bit more free time again.

Maybe you may help me with one problem:

Actually I am using a quite stupid cache mechanism to minimize screen 
refreshes. Its a simply compare bit by bit of the new and old 
framebuffer. Finally the RPI is redrawing only a rectangle with pixels 
changed.

My ides is to set a window of interest always when the RISC5 processor 
is accessing the RISC5 framebuffer address range. I am not sure if its 
more "cost effective" because any video access needs at least 2..3 more 
compare operations.

Can be also tested with the original emulator of Peter.

By the way, I believe Peters keyboard emulator is more complicated as 
necessary.

If you try to test Oberon on Ultibo, please don't forget to use an USB 
hub for the mouse and/or keyboard.

Regards

Markus