Radeon X700 Pro can no longer do AGP 8X since commit 295823d0879a

Michel Dänzer michel at tungstengraphics.com
Fri Sep 14 01:34:23 PDT 2007

On Fri, 2007-09-14 at 04:06 -0400, Sean wrote:
> With both 6.6.3 and 6.7.192 it shows as 4x.  However with 6.7.192 
> plus the hack forcing "is_v3" to true, the kernel reports success:
>   agpgart: Found an AGP 3.0 compliant device at 0000:00:00.0.
>   agpgart: Putting AGP V3 device at 0000:00:00.0 into 8x mode
>   agpgart: Putting AGP V3 device at 0000:01:00.0 into 8x mode
> So the question becomes, why does the driver decide v3 is not available,
> when the kernel and lspci both see otherwise?   Adding a debug display
> after the line in radeon_dri.c where it queries the value:
>   CARD32 agp_status = INREG(RADEON_AGP_STATUS) & mode;
> INREG(RADEON_AGP_STATUS) resolves to 0x4a0, and mode to 0x1f004a1b;
> so agp_status will always be 0, and is_v3 always false.
> Couldn't find any info on what the mode bits actually mean, but from the
> AGP3 spec it appears the AGP_STATUS should never have bit 7 set like it does
> here.  But beyond that i'm stumped.

Same here I'm afraid; maybe it's related to the AGP-to-PCIe bridge on
the card.

OTOH, can you measure any difference at all with 8x vs. 4x?

Earthling Michel Dänzer           |          http://tungstengraphics.com
Libre software enthusiast         |          Debian, X and DRI developer

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