[rescue] Re: SGI Onyx4 - uses ATI graphics chips (sigh)

Aaron Finley arnach at arnach.com
Fri Aug 22 13:56:38 CDT 2003

>If there is a bloody alpha channel in any image on the screen, it get
>bloody dropped when it hits the ramdac in the vast majority of normal
>circumstances.  Unless you happen to actually be using a platform where
>the alpha channel is transmitted down the wire in some analouge form as
>it leaves your computer, please stop mentioning it.  Yes they exist, but
>unless it is being used by the RAMDAC it isn't relevent.

It is relevant due to the fact that if the graphics subsystem lacks it or 
has a low bit alpha channel, then image quality and speed suffers. 
Compositing applications that have to use software alpha are very slow when 
it comes to any operations with transparency. Also if 24-bit graphics are 
using the channel, then it's typically 16-bit RGB and an 8-bit alpha, and 
the difference between 16-bit and 24-bit RGB is very visible.  

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