DRI on radeon 9500 using too wide memory bus?

Reid Linnemann lreid at cs.okstate.edu
Thu Mar 13 05:58:20 UTC 2008

I've had DRI running on a radeon 9500 for a while now, and at some point
in time tracking 6-STABLE and continuing now on 7-STABLE I've started
seeing rendering artifacts in gl in the form of a cross-hatch pattern of
pixels that don't get filled. At first I figured the card was failing,
but I remembered a fact about the 9500 that made me doublethink that.

The radeon 9500 is an r300 chipset, and differs from the 9700 only in
the width of the memory bus (128 bit vs 256 bit) and possibly clock
speed. If memory serves, the chip itself had the capacity to address 256
bits, but most 9500s just went out the door with 128 bit memory. I
remember at one point in time trying out a hack to the 9500 driver that
enabled the 256 bit bus to see if I had a rebadged 9700, and had similar

So I decided to peruse my X logs, and sure enough I see:
(--) RADEON(0): Mapped VideoRAM: 131072 kByte (256 bit DDR SDRAM)

Is it possible that the radeon driver is using the 256 bus? Is there a
way to force it to use a 128 bit bus? Has anyone else seen this?


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