The Amiga had a dedicated video chip (and it output vga signals which are fairly cheap).
This is a slow SPI bus with the cpu needing to push W x H x BPP pixels and with a 320x240 16bpp that comes out to 9 million bytes/sec for 60fps or 4.5 million for 30 fps.
Cortex M0 I believe has 4 cycles for load and store, so even if you had a perfect parallel 16 bit bus where you could do 1 load + 1 store to send a pixel, that comes out to a best case ~80 fps @ 100MHz with 100% cpu utilization (i.e you could do nothing else on that cpu, not even serve interrupts).
Another core wont help much because it shares the memory bus, and fill rate is the bottleneck here.
There's a good reason why we have dedicated chips for pushing framebuffer -> lcd physical pixels even back in the 80s.
This is a slow SPI bus with the cpu needing to push W x H x BPP pixels and with a 320x240 16bpp that comes out to 9 million bytes/sec for 60fps or 4.5 million for 30 fps. Cortex M0 I believe has 4 cycles for load and store, so even if you had a perfect parallel 16 bit bus where you could do 1 load + 1 store to send a pixel, that comes out to a best case ~80 fps @ 100MHz with 100% cpu utilization (i.e you could do nothing else on that cpu, not even serve interrupts). Another core wont help much because it shares the memory bus, and fill rate is the bottleneck here.
There's a good reason why we have dedicated chips for pushing framebuffer -> lcd physical pixels even back in the 80s.