We are currently shipping the file /etc/X11/Xsession.d/65mesa-check-x86-64 that disables ASM optimizations on 64bit Ubuntu if using an Intel CPU, as per bug #87661 , but this is already fixed on the version of Mesa in Karmic (see http://cgit.freedesktop.org/mesa/mesa/commit/?id=2b8d8989fb6f9c36baf166fc715182a1407ebadb ).
So, this file should be deleted from current distribution.
ProblemType: Bug
Architecture: amd64
Date: Sun Oct 25 23:50:17 2009
DistroRelease: Ubuntu 9.10
MachineType: Dell Inc. Vostro1310
Package: libgl1-mesa-dri 7.6.0-1ubuntu4
ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.31-14-generic root=UUID=0fc29d2a-1dce-4c7f-9c7d-0883e57053b0 ro rootfstype=ext4 quiet splash
ProcEnviron:
LANGUAGE=en_US.UTF-8
PATH=(custom, user)
LANG=en_US.UTF-8
SHELL=/bin/bash
ProcVersionSignature: Ubuntu 2.6.31-14.48-generic
RelatedPackageVersions:
xserver-xorg 1:7.4+3ubuntu7
libgl1-mesa-glx 7.6.0-1ubuntu4
libdrm2 2.4.14-1ubuntu1
xserver-xorg-video-intel 2:2.9.0-1ubuntu2
xserver-xorg-video-ati N/A
SourcePackage: mesa
Uname: Linux 2.6.31-14-generic x86_64
dmi.bios.date: 03/18/2009
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A15
dmi.board.name: 0H528C
dmi.board.vendor: Dell Inc.
dmi.chassis.type: 8
dmi.chassis.vendor: Dell Inc.
dmi.chassis.version: N/A
dmi.modalias: dmi:bvnDellInc.:bvrA15:bd03/18/2009:svnDellInc.:pnVostro1310:pvrNull:rvnDellInc.:rn0H528C:rvr:cvnDellInc.:ct8:cvrN/A:
dmi.product.name: Vostro1310
dmi.product.version: Null
dmi.sys.vendor: Dell Inc.
fglrx: Not loaded
system:
distro: Ubuntu
architecture: x86_64kernel: 2.6.31-14-generic
Unfortunately this looks like a bug where a very old (intrepid?) Xsession script didnt get removed on upgrade even though it was removed from the packaging and hasn't been shipped in over a year. It is safe to delete the file in the meantime until it gets fixed though.