From: "H. Peter Anvin" <hpa@zytor.com>
To: Chris Adams <cmadams@hiwaay.net>
Cc: linux-kernel@vger.kernel.org
Subject: Re: AGP aperture beyond 4GB not valid?
Date: Tue, 12 Aug 2008 23:01:18 -0700 [thread overview]
Message-ID: <48A278AE.1070800@zytor.com> (raw)
In-Reply-To: <20080813013255.GD633804@hiwaay.net>
Chris Adams wrote:
>
> Checking aperture...
> Node 0: aperture @ 1006000000 size 32 MB
> Aperture beyond 4GB. Ignoring.
> No AGP bridge found
> Your BIOS doesn't leave a aperture memory hole
> Please enable the IOMMU option in the BIOS setup
> This costs you 64 MB of RAM
> Mapping aperture over 65536 KB of RAM @ c000000
> PM: Registered nosave memory: 000000000c000000 - 0000000010000000
>
>
> My BIOS doesn't have an IOMMU option (latest BIOS available for the
> mboard). However, it appears that an aperture is allocated but the
> kernel then ignores it due to where it is placed. Why?
>
You can't use it as an IOMMU to handle 32-bit devices, since it's above
the 32-bit addressible region. Hence the kernel doesn't use it.
-hpa
prev parent reply other threads:[~2008-08-13 6:01 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-13 1:32 AGP aperture beyond 4GB not valid? Chris Adams
2008-08-13 2:38 ` Andi Kleen
2008-08-13 6:01 ` H. Peter Anvin [this message]
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