Re: Should I845 chipset support accelerated 3D?

["Mike A. Harris" <mharris www linux org uk>]

On 22 May 2003, Jason L Tibbitts III wrote:

>For some reason I thought that a machine with an I845 chipset should
>have hardware accelerated 3D, but mine don't seem to support it (with
>a stock Red Hat 9 installation and XFree packages updated to 4.3.0-6).

Yes, and it works too.

>Before I spend time trying to figure out why, could someone fill me in
>on what's expected to work with this chipset?  I know AGP memory
>allocation is working (X allocates 32MB of RAM) and DRI seems to load,
>but 3D is slow and redhat-config-xfree86 greys out the "enable
>hardware acceleration" checkbox.

The 3D accel checkbox is f'd up, and unfortunately it isn't 
something fixable without very major infrastructural work.  
Basically the config tool has no idea what specific chips XFree86 
supports 3D acceleration on, and there is no way to know, other 
than to go through the source code driver by driver and make a 
PCI ID list of them all, then put it hard coded into the config 
tool, or add a new field in the "Cards" database indicating which 
cards are DRI supported and which aren't.  That is a long and 
arduous task to perform, and would be an additional maintenance 
nightmare to maintain and keep up to date, so that isn't likely 
to happen.  It is the only way however to have an accurate 3D 
checkbox.

The current code has a hard coded list of drivers which contain 
support for 3D for at least one chip.  The list is not correct 
nor is it complete.  The problem is, a given driver might support 
30 chips, but might only support 3D on 1 chip, 5 chips, 10 chips, 
etc.  So by adding "radeon" to the list of drivers to permit the 
3D button to be enabled/disabled, it is then present on *ALL* 
radeon hardware, even Radeon hardware X doesn't support 3D on.

So, the choices we can do are:

1) Make the config tool hard code *every* driver that has any 
   form of DRI support for at least one chip.  The problem being 
   that even chips without 3D support will end up with the 3D 
   checkbox allowing people to turn it on and off, and resulting 
   in no difference as 3D isn't supported.

2) make the config tool have a hard coded list of all PCI IDs 
   which 3D is supported on, or via a database of some kind.  
   Long arduous task to create and then to maintain.

3) Remove the "Enable 3D" checkbox from the tool entirely, since 
   it is totally inaccurate, and not easily solved.

4) Add a comment there that this feature only works if X actually 
   supports 3D on the given card.


Nonetheless, XFree86 4.3.0 does support 3D on i845 and it should 
work as long as DRI is enabled in the config file.

-- 
Mike A. Harris