Public bug reported:
Binary package hint: linux-source-2.6.20
I'm using a Mac Pro running Feisty (2007/03/26), which was previously
running Edgy. There is a single WD Raptor disk in the box and when
2.6.20-12 boots it prefers the ata_piix driver instead of AHCI, which
causes high CPU usage when the disk is busy. It's also slower
(especially in one pathological case with Eclipse/Java 6/xfs). Edgy's
2.6.17 kernel correctly used the AHCI driver. I don't know if this is a
regression or a policy decision for Feisty.
Although I'm not using the actual Boot Camp application to start Linux
(I just formatted the disk PC-style and put GRUB on it and it magically
boots), it's probably correct to say I'm using the Boot Camp BIOS
emulation in the Mac's firmware. As far as I know there isn't a way to
make the BIOS/firmware set up the disk in AHCI mode, so it's up to Linux
to detect this correctly. Edgy used to, with the drawback that my DVD-
ROM didn't work right.
I have now unplugged my DVD-ROM drive from the power and IDE cables to
simplify things (I would rather have my disk speed back).
I'll attach two dmesg outputs. One is from Edgy with 2.6.17-10-generic
and one is from Feisty with 2.6.20-12-generic. I can't test 2.6.20-13
now (see bug 96480).
I think my PATA/SATA controller suffers from the Intel "combined mode"
driver detection problem that has been addressed in newer kernels.
Maybe there's a fix to backport.
** Affects: linux-source-2.6.20 (Ubuntu)
Importance: Undecided
Status: Unconfirmed
--
ata_piix used instead of AHCI for Mac Pro
https://launchpad.net/bugs/96692
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