On Tue, 2002-07-23 at 22:54, hy0 wrote:
> > If you set ForcePCIMode on any other architecture, DRI support will be
> > disabled.
> > (FIXME: I'm probably misunderstanding this option. How would one
> > force an AGP Radeon card to work on the PCI bus? Or a PCI Radeon card
> > (are there any?) to work on the AGP bus? Are there "dual-bus"
> > integrated Radeon cards floating around, which can sit on either the
> > PCI or AGP bus?)
>
> For AGP board, you can force it to use PCI GART instead of default AGP GART.
> This option can be used in following cases:
> (1) You have a PCI card.
PCI GART will be used automatically in that case.
> (2) You have an AGP card, but the agpgart kernel driver doesn't support the
> AGP bridge chipset on your motherboard.
Ditto.
> (3) The AGP GART doesn't work correctly.
> I'm not sure the current status of pcigart support. It didn't work reliably
> a few month ago.
Still doesn't seem to work on x86 but works fine on alpha and powerpc at
least. Weird.
I still think we should consider carefully if we want to document these
options.
> > AGPMode
> > Legal values for the AGPMode Option are 1 through 4 inclusive. (Note that
> > although 3 is accepted as a legal value, very few systems will support
> it.)
> > (FIXME: on PCs, does XFree86 actually override the AGP mode as set in
> > the system BIOS?)
>
> During initialization, 2D driver calls into the kernel agpgart driver to set
> specified AGP mode. There is no 3x AGP mode. If you set it to 3, the agpgart
> kernel driver will set it to 2x.
Actually, the value of this option is processed in this switch
statement:
switch (info->agpMode) {
case 4: mode |= RADEON_AGP_4X_MODE;
case 2: mode |= RADEON_AGP_2X_MODE;
case 1: default: mode |= RADEON_AGP_1X_MODE;
}
As you can see, anything except 2 and 4 will set 1x. Even 4 and 2 may
fall back to lower transfer rates depending on the capabilities of the
chip and the AGP bridge. agpgart handles that.
--
Earthling Michel D�nzer (MrCooper)/ Debian GNU/Linux (powerpc) developer
XFree86 and DRI project member / CS student, Free Software enthusiast
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