Racing the beam
Synchronising the processor to the exact position of the electron beam, changing graphics registers line by line as the screen is drawn.
The Atari 2600 (1977) had almost no frame buffer at all — just registers for a couple of objects — so the CPU was forced to feed graphics in lockstep with the cathode beam sweeping the tube, one line at a time. Miss the timing and the picture breaks. The phrase also became the title of Montfort and Bogost's book on the console (2009). The same idea drives raster interrupts and mid-line tricks on the C64 and Amiga: more sprites than the hardware promises, raster bars and opened borders all come from chasing the beam.