# SOLVED: Have I lost one core of my processor?

## gw

I'm using gentoo on a sony vaio laptop that has this Intel processor:

 *Quote:*   

> Intel® Core™ Duo Prozessor T2300

 

So this thing ought to have two separate processor cores, right?

Yet it seems that since some time gentoo only sees one core: if i do a

```
sensors
```

 it shows only the temp of one single core:

 *Quote:*   

> 
> 
> coretemp-isa-0000
> 
> Adapter: ISA adapter
> ...

 

Also 

```
 cat /proc/cpuinfo
```

gives

 *Quote:*   

> 
> 
> processor	: 0
> 
> vendor_id	: GenuineIntel
> ...

 

also showing just one core.

In the kernel config (Processor type and features) I tried "Core 2/newer Xeon" and "Pentium-4 M" but that didn't change the display of /proc/cpuinfo

What might be the problem?

Thanks

gwLast edited by gw on Thu Jan 31, 2008 2:11 pm; edited 2 times in total

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## nixnut

Did you enable SMP support in your kernel?

----------

## GODhack

Your problem wrog kernel. Standart kernel use only one core.

You need kernel-smp

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## i92guboj

 *GODhack wrote:*   

> Your problem wrog kernel. Standart kernel use only one core.
> 
> You need kernel-smp

 

Mmmm? There's no such thing in Gentoo.

The kernel is always the same, you get what you compile. Just make menuconfig to edit your kernel config, enable smp, compile, install and boot it. check the version and compilation date after booting with uname -a (just to make sure you booted the right kernel), and then try again. Your second core should be there.

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## GODhack

Ok I forgot to mention that you have to make kernel-smp yourself.

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## gw

Thanks for your smp hint, but I had that:

```

zcat /proc/config.gz| grep -i smp     

CONFIG_X86_SMP=y

CONFIG_SMP=y

# CONFIG_X86_BIGSMP is not set

# CONFIG_X86_VSMP is not set

CONFIG_PM_SLEEP_SMP=y

CONFIG_SUSPEND_SMP_POSSIBLE=y

CONFIG_HIBERNATION_SMP_POSSIBLE=y

CONFIG_X86_FIND_SMP_CONFIG=y

```

Also with uname -a:

 *Quote:*   

> Linux box 2.6.24-gentoo #3 SMP Sun Jan 27 11:43:54 CET 2008 i686 Genuine Intel(R) CPU T2300 @ 1.66GHz GenuineIntel GNU/Linux

 

Could it be that this is related to the newly introduced Control Groups, as I activated all this stuff in kernel config:

```

 zcat /proc/config.gz| grep -i cgroup                                                              [14:52]

CONFIG_CGROUPS=y

CONFIG_CGROUP_DEBUG=y

CONFIG_CGROUP_NS=y

CONFIG_FAIR_CGROUP_SCHED=y

CONFIG_CGROUP_CPUACCT=y

```

Two cores were recognized earlier, as I remember to have seen two core temps from the xsensors app.

Thanks for any hints.

gw

edit by nixnut: merged post back here. Mind the report button   :Wink:  

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## mimosinnet

I have a:

```
# uname -a

Linux joanet 2.6.23-gentoo-r3 #11 SMP Thu Jan 24 08:49:57 CET 2008 i686 Intel(R) Core(TM)2 Duo CPU T5450 @ 1.66GHz GenuineIntel GNU/Linux
```

and my two cores are recognised. I have compared your configuration with mine, and it is the same except the Control Groups, as they do not appear in the 2.6.23 kernel.

----------

## gw

 *mimosinnet wrote:*   

> I have a:
> 
> ```
> # uname -a
> 
> ...

 

Besides /proc/cpuinfo, how can I reliably determine how many cores the OS/kernel is seeing? Is there any app showing the load on each core during tasks?

Thanks

gw

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## MostAwesomeDude

 *gw wrote:*   

> Besides /proc/cpuinfo, how can I reliably determine how many cores the OS/kernel is seeing? Is there any app showing the load on each core during tasks?
> 
> Thanks
> 
> gw

 

I like htop.

----------

## mimosinnet

 *gw wrote:*   

> Besides /proc/cpuinfo, how can I reliably determine how many cores the OS/kernel is seeing? Is there any app showing the load on each core during tasks?

 

Have you tried to uncheck the "Control Groups" options? In this thread NeddySeagoon says:

 *NeddySeagoon wrote:*   

> 8086,
> 
> ```
> General setup -> Control Group support
> 
> ...

 

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## robdd

Hi gw - have you looked at the boot messages using dmesg ?  I have a relatively new desktop with an Intel motherboard, and initially when I booted the kernel was only recognising one of the two cores

Here's a section of my dmesg output, showing the bit where the kernel recognises the two CPUs:

```

ACPI: PM-Timer IO Port: 0x408

ACPI: Local APIC address 0xfee00000

ACPI: LAPIC (acpi_id[0x01] lapic_id[0x00] enabled)

Processor #0 (Bootup-CPU)

ACPI: LAPIC (acpi_id[0x02] lapic_id[0x01] enabled)

Processor #1

ACPI: LAPIC (acpi_id[0x03] lapic_id[0x82] disabled)

ACPI: LAPIC (acpi_id[0x04] lapic_id[0x83] disabled)

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

ACPI: LAPIC_NMI (acpi_id[0x02] dfl dfl lint[0x1])

ACPI: IOAPIC (id[0x02] address[0xfec00000] gsi_base[0])

IOAPIC[0]: apic_id 2, address 0xfec00000, GSI 0-23

ACPI: INT_SRC_OVR (bus 0 bus_irq 0 global_irq 2 dfl dfl)

ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 high level)

ACPI: IRQ0 used by override.

ACPI: IRQ2 used by override.

ACPI: IRQ9 used by override.

Setting APIC routing to flat

Using ACPI (MADT) for SMP configuration information

swsusp: Registered nosave memory region: 000000000009f000 - 00000000000a0000

swsusp: Registered nosave memory region: 00000000000a0000 - 00000000000e0000

swsusp: Registered nosave memory region: 00000000000e0000 - 0000000000100000

swsusp: Registered nosave memory region: 000000007e411000 - 000000007e413000

swsusp: Registered nosave memory region: 000000007e51e000 - 000000007e5ea000

swsusp: Registered nosave memory region: 000000007e5ee000 - 000000007e5f3000

swsusp: Registered nosave memory region: 000000007e5f4000 - 000000007e5ff000

Allocating PCI resources starting at 80000000 (gap: 7f000000:71000000)

SMP: Allowing 2 CPUs, 0 hotplug CPUs

PERCPU: Allocating 30504 bytes of per cpu data

```

(WTF does all that mean ??  :Smile:  )

If that's the problem please post the section of the dmesg output, and I'll think back to how I fixed my problem.

I *do* remember that initially, before I fixed whatever it was, I had to boot with the following boot option in grub..

```

kernel (hd0,0)/boot/bzImage root=/dev/sda1 pci=nommconf

```

So if that fixes it you're half way there.

Good luck - Rob.

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## gw

Thanks mimosinnet and robdd for your replies; I tried out all the variants (deactivating cgroups, the nommconf switch, even installing a fresh vanilla kernel), none of them brought my second core back.

Can it be that the processor is physically broken, how could I check that, and would it then run at all on  only one core?

Here's the relevant dmesg log, three snippets:

 *Quote:*   

> 
> 
> [    0.000000] ACPI: SSDT 3FE8BEE2, 07CB (r1   Sony       N0 20060710 PTL  20050624)
> 
> [    0.000000] ACPI: SSDT 3FE8BD3A, 01A8 (r1   Sony       N0 20060710 PTL  20050624)
> ...

 

So only one core is found.

gw

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## desultory

Have you tried booting an SMP aware live CD, or the equivalent thereof?

----------

## jcat

What does your BIOS say? Does it believe you have 2 cores?

Cheers,

jcat

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## robdd

gw said:

 *Quote:*   

> 
> 
> Can it be that the processor is physically broken, how could I check that, and would it then run at all on only one core? 
> 
> 

 

I may be banned from the gentoo forums for suggesting this   :Very Happy:   but did your laptop come with Windoze ?  If you set it up with dual boot or you have the Windoze install discs then you can boot into Windoze and run Task Manager (right click on the bottom task bar, and select Task manager from the menu). On the performance tab of Task Manger there's a CPU load graph at the top. If you have dual processors then there will be two graphs, and if you start some CPU-intensive application you should see both cores being used. This really is a "last ditch" suggestion - if you have access to a live CD then it would probably be quicker to try that.

I don't blame you for feeling p***ed off !! I felt the same when I booted up the first time and found I could only use one core when I'd paid for two.

BTW - if you do get both cores running you can try xosview, which will show nice graphs of the load on each core. (Then you'll see that instead of your old computer's single core spending 99.9999999% of its time running the idle loop and screensaver your new one will use one core to run the idle loop/screensaver and the other will be completely idle   :Sad:  )

Regards, Rob

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## gw

 *jcat wrote:*   

> What does your BIOS say? Does it believe you have 2 cores?
> 
> Cheers,
> 
> jcat

 

Guys, this is the weirdest thing!

First thanks to desultory, jcat, robdd and all those who replied.

I went on trying, with three different smp aware live CD and also booting into windows; all of them showed only on core present.

The sony vaio vgn/sz bios is in itself totally useless; pratically no options to chose from and no hardware info at all. Also I updated it about a year ago, without any problems.

As a last ditch effort, I re-downloaded this same bios update from sony and tried to reinstall it. That was impossible, as a message popped up saying it is already the newest version. 

I then went into bios config and did a "reset default values". The only setting that was then reset, was the speaker level (as I said not much to set at all).

Yet then, on rebooting into linux, all two cores magically reappeared, I've got now about the same dmesg that robdd posted.

So to sum up: in what strange way ever, this seems to have been a bios related problem; as the bios gives no information at all, it is difficult to find out what was happening.

BTW: this bios seems to be in DAU mode, keeping all the info away from the user. Does anyone know if that could be the case, and how to change it?

Thanks again for your assistence

gw

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## jcat

Good news!   :Cool: 

I'm sure there is a way to access ALL your BIOS features, but I don't know what it would be.  At least the issue has been resolved!   :Smile: 

Cheers,

jcat

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