I observed the same kind of defect on an AMD Phenom 9550 Quad Core: most of the time only one CPU is recognized and the others are indicated as "not responding", and sometimes all four are present. Disabling or enabling ACPI does not change anything, the cores are not more often recognized.
One thing that changed the deal was to switch off the Ubuntu splash boot and disable any kind of VGA=xxx line in the kernel arguments. For some reason the boot process is much faster that way and has always caught all four CPUs so far, but that probably needs more experimentation. N. -- Usually misses 2nd processor https://bugs.launchpad.net/bugs/97554 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs