Only one core working on dual core CPU

[Adam Bagnall]

Binary package hint: linux-image-2.6.24-15-generic

This bug was present in Gutsy, I upgraded to Hardy to see if it had been resolved but it is still present. I have an AMD Athlon64 x2 5600+, which worked fine on my previous motherboard. I changed my motherboard to an ECS AMD690GM-M2 and now only one core works in Ubuntu, both cores are recognised in Windows. I have tried various things found via google. Booting with noapic makes no difference. acpi=off and acpi=ht result in an unbootable system. Disabling HPET in the bios makes no difference.

[Adam Bagnall (bagnaj97)]

Under Hardy 64bit daily (11/04/08) both cores are detected, still an issue on 32bit.

[Leann Ogasawara (leannogasawara)]

The Ubuntu Kernel Team is planning to move to the 2.6.27 kernel for the upcoming Intrepid Ibex 8.10 release. As a result, the kernel team would appreciate it if you could please test this newer 2.6.27 Ubuntu kernel. There are one of two ways you should be able to test:

1) If you are comfortable installing packages on your own, the linux-image-2.6.27-* package is currently available for you to install and test.

--or--

2) The upcoming Alpha5 for Intrepid Ibex 8.10 will contain this newer 2.6.27 Ubuntu kernel. Alpha5 is set to be released Thursday Sept 4. Please watch http://www.ubuntu.com/testing for Alpha5 to be announced. You should then be able to test via a LiveCD.

Please let us know immediately if this newer 2.6.27 kernel resolves the bug reported here or if the issue remains. More importantly, please open a new bug report for each new bug/regression introduced by the 2.6.27 kernel and tag the bug report with 'linux-2.6.27'. Also, please specifically note if the issue does or does not appear in the 2.6.26 kernel. Thanks again, we really appreicate your help and feedback.

[Adam Bagnall (bagnaj97)]

I've tested this evening with Intrepid daily-live 04-Aug-08 and both cores were working under 32bit. The problem still exists with the latest Hardy kernel.

[Vishal Rao (vishalrao)]

Same problem here with Intrepid Alpha 5 (amd64 kernel .27-2.3). Was not a problem with Hardy amd64 (latest) or Intrepid Alpha 4 previous amd64 kernel.

Hardware is HP Pavilion tx1302au Tablet PC with AMD Turion 64 TL-58 dual core 1.9 ghz CPU with nVidia Go 6150 motherboard.

I need to specify the "nolapic" option to get this to boot on Intrepid Alpha 5 with latest updates. gnome system monitor also shows single cpu.

Will attach dmesg, lspci and cpuinfo...

[Vishal Rao (vishalrao)]

Updated Ibex today and the issue no longer exists for me. I also don't need to specify the nolapic option at boot time either.

[Leann Ogasawara (leannogasawara)]

Thanks for the update. Adam, can you comment if this is fixed for you with the most recent Intrepid updates? Thanks.

[Adam Bagnall (bagnaj97)]

As stated on 2008-09-05 this is now fixed in Intrepid (both i686 and amd64). Hardy i386 still has the issue even with the latest updates.

[Paulo Dias (paulo-miguel-dias)]

I'm experiencing the same problem with intrepid beta 1 and a turion tl-60 x2.. i need to activate nolapic in order to be able to suspend/resume (if i dont, it just hangs), BUT i loose a cpu. i suspect the resume/suspend failure is a smp issue, since it works fine with one cpu disable via nolapic.

[Leann Ogasawara (leannogasawara)]

@Paulo, care to open a new bug report as it seems you have different hardware than the orignal bug reporter and Adam has commented this is resolved for Intrepid.

[Trey Blancher (ectospasm)]

I get this problem about 85% of the time in Intrepid, and I haven't narrowed down the magic that brings up all four cores. It worked flawlessly for weeks, and downgrading to 2.6.27-9 from 2.6.27-11 didn't bring back all of my cores.