HudsonArcade
Well-known member
That would make sense if the two banks of RAM are interleaved from top to bottom where the top 4 lines of characters are rendered from bank 1 and the second 4 lines from bank 2, etc.
Bank1-A (Top of Screen)
Bank2-A
Bank1-B
Bank2-B
Bank1-C
Bank2-C
Bank1-D
Bank2-D (Bottom)
If the chip select was stuck, it would render the same bank twice.
Bank1-A (Top of Screen)
Bank1-A
Bank1-B
Bank1-B
Bank1-C
Bank1-C
Bank1-D
Bank1-D (Bottom)
They not.
Odd rows are in one bank, even in the other.
A0 drives the bank select logic:

