These are all good stepping stones though, I wouldn't overthink it too much as until you actually build something, you're not necessarily making good decisions anyway. I learn most by doing, so my approach is to think of something, build it, fix it, and keep iterating. Sometimes you need to go back ...

On the BBC, in modes 4-7, the video circuit actually only needs to fetch from RAM at half the CPU clock rate (i.e. 1MHz). But in MODES 0-3, it does need all 2MHz to pull enough data from RAM to drive the display. Edit: The maths for this is, e.g. for MODE 0 (640x256x50Hz) - there are 50 frames per ...

I don't quite understand your last paragraph. The video subsystem is not much more sophisticated than a shift register, so a byte needs to be fetched each time a byte is needed - for 8, 4, or 2 pixels worth of bits.

Sorry, I'll try and clarify what I mean:

* On the beeb, the CPU is at 2Mhz and ...

Disclaimer: I'm not actually trying to build a project here, this is just something I'm interested in understanding!

In the BBC Micro, the graphics framebuffer data was stored within the main system RAM. To extract it, the RAM was run at twice the clock speed of the CPU, so the graphics hardware ...