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Old 01-05-04, 06:23 PM   #1
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Join Date: Jan 2004
Posts: 2
Default 4496 on x86_64 w/8G RAM; IOMMU/AGP problems?

Hello all --

I've read this thread with some interest. We're running a somewhat bleeding
edge setup, and we're having problems with the nvidia drivers. Here's the

* The box is a dual opteron (246) w/8G RAM
* The card is a GeForce2 GTS/GeForce2 Pro
* Running RHEL 3.0 AS x86_64
* The disk is a SATA drive, which means we have to run kernel 2.6.0
* Kernel is patched with mm1 and Andi Kleen's x86_64 patchset

We're trying to use the 4496 drivers (yes, we applied the
patches), but they lock the system hard. People have recommended
using kernel parameters (such as noapic, acpi=off, etc.), but nothing
that we've tried has worked. This was all trying to use agpgart compiled
directly into the kernel.

The problem may be with IOMMU. Since the nvidia drivers lock hard with
the AGPGART kernel module compiled into the kernel, we decided to try
disabling it with NVAGP "1". No problem, except that AGPGART is
forced to be on if IOMMU is enabled. IOMMU should be enabled on
systems with more than 4G of RAM to make sure that certain older 32-bit
PCI cards work.

So, the problem is this: we have more than 4G of RAM, so we we have to
disable IOMMU to disable AGPGART, but even after we've done all of that,
the nvidia drivers hang hard.

Of course, disabling IOMMU could be what's causing the driver to hang.
The docs say that IOMMU is necessary for PCI cards that don't
support DAC.



I'm way in over my head.

Any ideas? Does anyone know if this is an IOMMU problem? Is it
the fact that the card is old? Are there any more patchsets that
people would recommend? (I see that the mm2 patchset is out; I
may try that).

Any help would be appreciated.


-- David
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