Perhaps you meant Vsync.
Simply put, Vertical Synchronization locks your game framerate to your monitor's refresh rate. What this means is that if your game (normally) goes beyond 60 FPS and your refresh rate is 60Hz, then your game will be locked at 60 FPS. Do note that if your game is locked at 30 FPS and your refresh rate is 60Hz, you will not make your game jump to 60 FPS. The main goal is to ensure smooth framerate.
And I think VSync has been in HiAlgo BOOST for awhile now.
And a Q/A from the main site:
Q: I GET TERRIBLE HORIZONTAL FLICKERING LINES WHEN TURNING.
Q: I GET SCREEN TEARING, EVEN IF I PRESS F10 TO TURN HIALGO OFF...
You see tearing, because by default HiAlgoBoost turns VSYNC off (to get better performance). In most cases the tearing is hardly noticeable, but if your framerate is around 60fps, it may be annoying. In this case set NO_VSYNC to false in HiAlgoBoost.ini.
Source : http://www.hialgo.com/SkyrimFAQ.htm