Direct Render or VSync ?

[PhilT]

Just a simple question . In the System Settings, Desktop Effects, Advanced tab you can enable Direct Rendering or use VSync (or both). What is the real difference or advantage in using either?

The situation is this - When running GLXGEARS in a console I get 2150 f.p.s. with VSync; but only 1220 f.p.s. with direct rendering enabled; should I stick to VSync? Does it matter?

My system has: Intel Dual-Core E7400 (2x2.8GHz) processor; 4Gb XMS2 800mHz RAM, 512 MB Radeon HD 3650 PCI Express Graphics Card. I'm running a Kubuntu 9.04; KDE 4.3; 64-bit system; I compiled the ATI graphics FGLRX drivers for my setup; it flies very well. I just don't understand what all the choices mean.

Thanks for any pointers!

[Snowhog]

Re: Direct Render or VSync ?

Some explanation here.

[PhilT]

Re: Direct Render or VSync ?

Thanks Snowhog. I already read that just a few minutes ago! The advice seems mixed, and mostly seems to affect worried gamers! I'm not one of those. If there's no real advantage either way I guess it doesn't matter which settings to use. I get good 3D acceleration with both. It was just an information question but I suppose one needs to be a graphics or electronics expert to understand the ramifications.

[Snowhog]

Re: Direct Render or VSync ?

I'm not a gamer either, but I understand 'generally' about vsync, which limits the framerate of your graphics card to no more than your monitors refresh rate.

I opt for the selection that gives me the fastest frame rate in glxgears.

[abalone]

Re: Direct Render or VSync ?

What's fast, though? I suppose it doesn't really matter to most non-gamers, but the OP's glxgears frame rate does seem rather low to me. Even my own seems low to me; people with even older setups than mine seem to get several times the FPS out of glxgears. (I get ~4800 with compositing, ~11900 without. That's on an AMD X2 4800+ system (32 bit Kubuntu 9.04) with a 512 MB Geforce 7950 GT (AGP!), 3 GB RAM (DDR1!) and whatever version the Nvidia drivers in the repositories are. It used to be higher, though I don't know if that was in KDE 4.)

I used to enable vsync (or sync to v(ertical )blank, which I suppose is the same) in Nvidia Settings because I got pretty bad tearing effects otherwise. I still do, on the right monitor, and it doesn't seem to matter anymore what I enable or disable. Not sure if it's to do with KDE 4 or if I need to load the settings at some other point. Meh.