Ubuntu 8.10 IOMMU
Since I installed Ubuntu Intrebid Ibex and upgraded my RAM to 4 gigs, i have been getting something like this message at boot:
[ 0.004000] Checking aperture…
[ 0.004000] No AGP bridge found
[ 0.004000] Node 0: aperture @ 20000000 size 32 MB
[ 0.004000] Aperture pointing to e820 RAM. Ignoring.
[ 0.004000] Your BIOS doesn’t leave a aperture memory hole
[ 0.004000] Please enable the IOMMU option in the BIOS setup
[ 0.004000] This costs you 64 MB of RAM
[ 0.004000] Mapping aperture over 65536 KB of RAM @ 20000000
So I searched the ubuntuforums for the solution to this, and it was pretty simple:
add iommu=noaperture to the kernel line in your /boot/grub/menu.list file. When You reboot, you will no longer get the error message.
If the above solution doesn’t work, try iommu=soft instead.
This is on 64bit Ubuntu 8.10 with an AMD Turion x2 processor and ATI chipset / graphics. Acer Aspire 5100 series.
majµcarma, 
Brenan 7:54 pm on December 13, 2008 Permalink
Thanks for posting this. I had been searching on google for a good while and I finally stumbled upon your post. The iommu=noaperture worked for me – ubuntu 64bit, AMD Phenom 9850 BE and Asus Mobo (790FX chipset)
magnusium 10:23 pm on December 13, 2008 Permalink
I’m glad you found it useful.
zappafan 6:59 am on December 15, 2008 Permalink
Thanks from me, too. I have an ASUS M2N-SLI Mobo, Ubuntu 8.10 64bit, 4GB, Athlon 64×2 5600+. I found something also on the ASUSTeK support site that sent me here:
ftp://download.nvidia.com/XFree86/Linux-x86/1.0-8174/README/32bit_html/appendix-l.html
Scroll down a bit and there’s an IOMMU section.
magnusium 7:57 am on December 15, 2008 Permalink
Thanks, this was educational.
quote:
On AMD’s AMD64 platform, the size of the IOMMU can be configured in the system BIOS or, if no IOMMU BIOS option is available, using the ‘iommu=memaper’ kernel parameter. This kernel parameter expects an order and instructs the Linux kernel to create an IOMMU of size 32MB^order overlapping physical memory. If the system’s default IOMMU is smaller than 64MB, the Linux kernel automatically replaces it with a 64MB IOMMU.
end quote
So this means that one can try iommu=memaper, if the noaperture and soft fails.
Sander 12:52 am on December 27, 2008 Permalink
Hi,
I think that by adding “iommu=…” only the message will go away, but you won’t get the 64 MB memory back.
Easy way to check: use “free -m” in both cases (with and without the option iommu=…), and see if there’s any difference.
Please let us know.
Sander 12:57 am on December 27, 2008 Permalink
PS:
There is some discussion and info on http://ubuntuforums.org/showthread.php?t=1018854
magnusium 11:57 am on December 27, 2008 Permalink
I’ll have to subsribe to that thread, I don’t have Ubuntu on my laptop right now, had to go to “that other OS” for a while. But it won’t be long before I put Ubuntu back on it.
My acer will not POST if I put the onboard graphics mem to less than 256 in my BIOS settings, tried it once and I had to rip out a stick of RAM to get back in to change the setting.
Speicherverwaltung und IOMMU Kernel 2.6.27-9 | Maltes Blog 12:51 am on January 21, 2009 Permalink
[...] http://rubbad.wordpress.com/2008/11/28/ubuntu-810-iommu/ [...]
majµcarma 1:47 pm on February 14, 2009 Permalink
Thank you for this post. I had the same problem last week.
ASUSTek ALiveNF7G-FullHD R3.0 + MSI 9500GT 1Gb / Atlhon 64 X2 6100+ 4Gb RAM