i have the same problem here with ubuntu 8.04 x86 desktop edition. only one core is viewed by the kernel as reported by /proc/cpuinfo or monitor application.
it works with a 2.6.24 kernel on ArchLinux http://www.archliunx.org ! so the big distro fail where the small ones do a better job. may be it has something to do with the DSDT acpi table. i see that there is one in use in ubuntu here while none for archlinux. i have a dell inspiron 531; athlon 64 x2 4400+, MCP61 chipset, -- Athlon X2 Dual Core Processor - Second CPU/Core not working with i386 kernel https://bugs.launchpad.net/bugs/213011 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