3 ms·

Would like to see this in a BBC Micro

• analog31 5y ago
  A challenge with any such project, is that most code running on the old micro's took the processor clock speed as an implied system constant. So, timing of things like video refresh, and sound, would become unworkable if you tried to change the clock speed. The Apple ][ had a very particular clock speed, to implement a video controller that shared the memory bus with the CPU. I know that I'm guilty of managing the timing of some peripherals by using loops full of NOP instructions. As processors have gained more hardware features such as sophisticated timers and memory controllers, it has become easier to write code that runs independently of the clock speed. In the case of old systems, it's probably possible but might require access to the original source code. Some early PC-compatible motherboards with higher clock speeds had a front panel switch, so you could run the machine at the old speed for software that needed it.