LinuxQuestions.org - Core 2 Duo U7500, One Core MIA

I'm running Gentoo on a Sony Vaio VGN-TZ170N, with a Core 2 Duo U7500. Recently, one of the cores seems to have vanished. It previously appeared in cpuinfo, gkrellm showed it working, and cpufreq created the
appropriate entries for it in /sys. I was tipped off to its disappearance by one of my startup scripts throwing an error when its /sys entry no longer existed. I have made no changes to my kernel in a month or so
and no packages have been updated aside from openssh and a couple of libraries.

Output of /proc/cpuinfo:

Code:

processor      : 0

vendor_id      : GenuineIntel

cpu family      : 6

model          : 15

model name      : Intel(R) Core(TM)2 CPU        U7500  @ 1.06GHz

stepping        : 2

cpu MHz        : 1067.000

cache size      : 2048 KB

physical id    : 0

siblings        : 1

core id        : 0

cpu cores      : 1

fdiv_bug        : no

hlt_bug        : no

f00f_bug        : no

coma_bug        : no

fpu            : yes

fpu_exception  : yes

cpuid level    : 10

wp              : yes

flags          : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc up arch_perfmon pebs bts pni monitor ds_cpl vmx est tm2

ssse3 cx16 xtpr lahf_lm

bogomips        : 2130.71

clflush size    : 64

I took a look at the output of dmesg and noticed this portion:

Code:

ACPI: BIOS bug: multiple APIC/MADT found, using 0

ACPI: If "acpi_apic_instance=2" works better, notify linux-acpi@vger.kernel.org

ACPI: DMI detected: Sony

ACPI: PM-Timer IO Port: 0x1008

ACPI: Local APIC address 0xfee00000

ACPI: LAPIC (acpi_id[0x00] lapic_id[0x00] enabled)

Processor #0 6:15 APIC version 20

ACPI: LAPIC (acpi_id[0x01] lapic_id[0x01] disabled)

ACPI: LAPIC_NMI (acpi_id[0x00] high edge lint[0x1])

ACPI: LAPIC_NMI (acpi_id[0x01] high edge lint[0x1])

I took that advice and added the parameter to my grub config.

New /proc/cpuinfo:

Code:

processor      : 0

vendor_id      : GenuineIntel

cpu family      : 6

model          : 15

model name      : Intel(R) Core(TM)2 CPU        U7500  @ 1.06GHz

stepping        : 2

cpu MHz        : 1067.000

cache size      : 2048 KB

physical id    : 0

siblings        : 2

core id        : 0

cpu cores      : 2

fdiv_bug        : no

hlt_bug        : no

f00f_bug        : no

coma_bug        : no

fpu            : yes

fpu_exception  : yes

cpuid level    : 10

wp              : yes

flags          : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm                    

bogomips        : 2130.72      

clflush size    : 64            

                                

processor      : 1            

vendor_id      : GenuineIntel  

cpu family      : 6            

model          : 15            

model name      : Intel(R) Core(TM)2 CPU        U7500  @ 1.06GHz

stepping        : 2            

cpu MHz        : 1064.038      

cache size      : 2048 KB      

physical id    : 0            

siblings        : 2            

core id        : 1            

cpu cores      : 2            

fdiv_bug        : no            

hlt_bug        : no            

f00f_bug        : no            

coma_bug        : no            

fpu            : yes          

fpu_exception  : yes          

cpuid level    : 10            

wp              : yes          

flags          : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc arch_perfmon pebs bts pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm                    

bogomips        : 2128.08      

clflush size    : 64

New dmesg output:

Code:

ACPI: BIOS bug: multiple APIC/MADT found, using 2

ACPI: If "acpi_apic_instance=0" works better, notify linux-acpi@vger.kernel.org

ACPI: DMI detected: Sony

ACPI: PM-Timer IO Port: 0x1008

ACPI: Local APIC address 0xfee00000

ACPI: LAPIC (acpi_id[0x00] lapic_id[0x00] enabled)

Processor #0 6:15 APIC version 20

ACPI: LAPIC (acpi_id[0x01] lapic_id[0x01] enabled)

Processor #1 6:15 APIC version 20

ACPI: LAPIC_NMI (acpi_id[0x00] high edge lint[0x1])

ACPI: LAPIC_NMI (acpi_id[0x01] high edge lint[0x1])

The second core has reappeared, and the kernel seems to be utilizing it, but cpufreq still won't create /sys entries for it. I'm posting here because I'm starting to suspect this a hardware failure, but I'm hoping it's something I did and just can't remember / work it out.

Thoughts?