Transparent themes without composition

Zack Rusin zack at
Sun May 3 03:53:15 CEST 2009

On Saturday 02 May 2009 19:32:28 David Nolden wrote:
> Am Sonntag 03 Mai 2009 00:20:13 schrieb Martin Gräßlin:
> > I very much doubt that any Linux distribution including KDE 4.3 will not
> > provide at least XRender compositing with any hardware. If you own such a
> > hardware you should report a bug report to X developers requesting
> > support.
> Intel GMA 955, any kind of composition is completely unusable on that
> hardware, even though the drivers are said to be the best. The hardware is
> simply not powerful enough to composite a whole desktop. Also I don't have
> any interest in discussing this issue.

So first you don't even have the time to check the name of the hardware you're 
referring to (Intel doesn't have a GMA with number 955), then you make a 
completely bogus statement (even the very first initial GMA 900 had were fully 
capable of doing fully composited desktops), and you top it off with a sissy fit 
saying you've got no interest discussing it? Classy.

I like math. Wanna do math? Lets do math!

Lets take the oldest Intel GMA, the 900.
The 900 operates at peak of 330MHz, 4 pixels in a clock cycle.
Therefore peak fill rate is: 330000000*4 = 1332000000 pixels per second
Lets say you have 1600x1200 resolution and your composition manager wants to 
do animation at 60fps, therefore:
1600*1200*60 = 115200000 pixels per second
So to do 1600x1200 at 60 frames per second our GPU needs to be able to push 
115200000 pixels per second. 

GMA can do 1332000000, therefore: 1332000000/115200000 = ~11.5

GMA 900 can work on 10x as many pixels as would be required!

Even if you don't use the builtin blending unit and blend in shaders directly 
and assume the worst case scenario of sampling from 2 surfaces (aka, operate 
on 2 pixels per clock) and do something crazy in your shader you're still well 
within 30-60fps, even for really funky effects.


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