Yes, there's only one display mode. But if anything it was better for displaying text than graphics.
The rows of pixels were laid out in a wacky fashion to make text rendering fast. The display resolution was 256x192. Being monochrome, the bitmap part of the display therefore used 32 bytes per row of pixels. You might expect that the second row would start at start_of_screen_address + 32. BUT NO! It was at start_of_screen_address + 256 because you can increment an address register by 256 faster than you can increment by 32 (on a Z80). Hahaha.
The result was that drawing graphics was a bit fiddly, but drawing 8-pixel wide character glyphs was easy and fast.
