Specus is the working title of a “Zeldroidania” game (basically a mix of Zelda and Castlevania).

Quote:

Right now all it does is load a map and let you scroll around it. The scrolling engine breaks up the name table updates over four frames, and updates a 16-pixel wide area during that time. That means this engine cannot handle scrolling faster than 4 pixels per frame. The same code path is used for both horizontal and vertical maps. Branches are taken to handle the differences.

http://nesdev.parodius.com/bbs/viewtopic.php?t=7765