[coldpie]

This is a great description of a commonly-used technique for splitting the screen in NES games that scroll smoothly. It may or may not have been intended, but this is a common technique for games that have a "status bar". Super Mario Bros 3 is another obvious example, but even Super Mario Bros uses it long before then for its top status bar. I first read about it in the excellent "I Am Error" book by Nathan Altice, but googling around for "nes sprite zero split" turns up plenty of other articles, too.

[einr]

Nitpicking, but SMB3 uses the MMC3 chip which "adds an IRQ timer to allow split screen scrolling without the sacrifice of sprite 0" (Wikipedia) so it does not use this technique.

SMB1 actually also does not use the sprite zero split technique because it never scrolls vertically. Its status bar is just a bunch of fixed background tiles.

[coldpie]

Ah, didn't know that about the MMC3!

Regarding SMB1, I'm quite sure it uses the sprite 0 thing to keep the status bar stationary while the level scrolls smoothly beneath it by setting the scroll register only after when the status bar is done drawing. See more thorough description here: https://retrocomputing.stackexchange.com/questions/1898/how-...

[papln]

The article is confusing. The headline/lede claim is about partial vertical scrolling. The middle is a long detour to partial horizontal scrolling (well documented, including SMB1), and then the end goes back to talk about partial vertical scrolling (Zelda).