Where is the video ram located in the TVC?
It is can be paged to Page 2 (8000-BFFFh). 16K in the 32K and 64K models and 64K in the 64K+ model. (This is a additional memory, then the total is 48K, 80K, and 128K).
Only In 64K+ model: additional register for select which 16K used by the CTRC, and which paged to the Z80. Also possible page video memory to Page 1 (4000-7FFFh).
How is the bitmap mode organsized? Does it encode the colours in bitmap mode in the same way like the EP (and CPC)?
Yes. (It is also exist a software TVC emulator for EP
)
My idea: 4 paging registers for Page 0-3. Bit 7 switch at the current page the internal/expansion accessing. Other bits select 16K pages, 128 pages possible=2MB (more than enought for SymbOS
)
When accessing screen, the Page 0,1,3 from the expansion, and Page 2 from the internal, where paged the video memory with the original paging registers.
What do you think?