[foxhill]

you don't need to "beam race" to achieve sub-frame latency - you don't need to be accurate. switching off vsync should, principally, be enough to achieve this.

otherwise, yes, modern APIs go out of their way to avoid the possibility of this (the dreaded "tearing" artifacts you see from the frame buffer being changed during the transmission of the video signal to the monitor). i don't believe older techniques like you've mentioned are at all possible today, and only really made sense to talk about when analogue displays were the norm.