amazoc"mat_forcehardwaresync" which IIRC defaults at value "1"
On PCs, the ConVar default is 1, however, the value for PCs is defined by the dxsupport configuration, so depending on your dxlevel and hardware, the value may be 0 or 1 by default.
amazoc-Value 0 does cause in some hw certain amount of input lag , specially in mice devices ,similar to vsync(commented below) or closely related , however I see a reversed situation there http://www.rage3d.com/Board/archive/index.php?t-33807316.html they affirm a value of 1 ,forcing vsync ,so does still confuse in layman terms.
No, it is not VSync. Hardware sync waits per frame for the GPU to execute the commands in the command buffer and then stops waiting if the execution takes too long. Sure, it is some extra work and waiting, but it prevents the hardware from drifting behind too many frames from what the engine has requested. Most of the performance impact of hardware syncing depends on how poorly the driver behaves, not the extra work done from hardware syncing alone. And as you can imagine, this is partially accounted for in the dxsupport configuration per device.
amazoc-Its used only along mat_vsync 1 and mat_queue 2 (multicore),otherwise it can be the cause of screen tearing problems.
-Does sync hw when treading .
VSync isn't related to it, so mat_vsync doesn't affect HW sync. The material system queue modes 0 and 1 directly call it at the beginning of the frame, while mode 2 calls it in a queued call (for threading reasons).
amazoc-In certain situations can cause graphical glitches or crashes,memory read exceptions , you can find documentation in steampowered dot com ,that in case of trouble they recommend setting this to '0' within the launch options of the specified game . -->https://support.steampowered.com/kb_article.php?ref=1274-uohk-5653 but doesnt give any in depth detail of it.
This depends on your drivers and hardware, and only happens in specific rendering situations. These errors happen when the frame sync query object is lost and the driver isn't able to recover properly. (again mostly accounted for in the dxsupport configuration per device).
amazoc**I dont see actually anywhere in your cfg this cvar set on or off .
Would appreciate much ,If you could clear the confusion and doubt by explaining and detailing in which situations this can work best or how this is hw-dependant and so where to be cautious when setting up it.
I hope my explanations above were sufficient enough to come to the conclusion that configs and users probably have no business setting this convar themselves. It is best to trust what Source thinks is best for your hardware and only if you find it problematic, you should you change the value.
Good question, by the way.