How to enable multicore?

[GaryB]

I have a 4 core AMD but lscpu shows only one. how would I fix this?

Thanks
Gary

[pavroo]

It happens if you installed 32 bit Sparky on multicore machine.
Run Sparky APTus -> Refresh package list, then Install tab -> Install 686-pae kernel.
Then reboot.

[Lizbeth]

Just curious, if one installed the 32 bit system, couldn't one then install the 64bit kernel and headers also and run from them?

[pavroo]

No, you can't.
I should be 32 bit (686-pae) kernel to handle multicore CPU and RAM bigger than 4 GB.

p.s.
It's possible but makes to many problems, I don't recommend it.

[GaryB]

When I do that I get the message

You are running 64 bit system!

then exits.

Thanks

[GaryB]

I went into my BIOS and made sure the cores were activated at boot, the boot mobo splash screen says 4 cores activated. I then booted up Kubuntu and lscpu says the same thing, 1 core.

[pavroo]

Are you sure you are running 64 bit system?
Check it out:

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uname -a

[GaryB]

uname -a returns this:

Linux debian 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt9-3 (2015-04-23) x86_64 GNU/Linux

[pavroo]

It looks like you have installed 64 bit system.
The big question is: does your CPU support multicore?
Can you check the CPU's maker specification?

[Wombat]

Showing up as single core may be the result of just not properly recognising the CPU by whatever the method linux uses ...the same
when  HWINFO encounters an unknown item and displays a wrong default result in windows...

[pavroo]

Show us:

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nproc
Count the number of "physical processor(s)"

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grep "physical id" /proc/cpuinfo | sort -u | wc -l
Count the number of "physical cores per CPU"

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grep "cpu cores" /proc/cpuinfo |sort -u |cut -d":" -f2
Count the number of "logical cores " (including multi-threading cores)

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grep -c "processor" /proc/cpuinfo

[MoroS]

You could post the contents of /proc/cmdline file. You just might be running with the "acpi=off" option, which tends to disable additional cores.

[GaryB]

garyb@debian:~$ nproc
1
garyb@debian:~$ grep "physical id" /proc/cpuinfo | sort -u | wc -l
1
garyb@debian:~$ grep "cpu cores" /proc/cpuinfo |sort -u |cut -d":" -f2
1
garyb@debian:~$ grep -c "processor" /proc/cpuinfo
1
garyb@debian:~$

[GaryB]

/proc/cmdline

BOOT_IMAGE=/boot/vmlinuz-3.16.0-4-amd64 root=UUID=cc17d4be-6875-4daa-965f-329ca3d66049 ro nolapic splash

[MoroS]

/proc/cmdline

BOOT_IMAGE=/boot/vmlinuz-3.16.0-4-amd64 root=UUID=cc17d4be-6875-4daa-965f-329ca3d66049 ro nolapic splash

Well, it's not "acpi=off", but still, the result's similar. The LAPIC is a Local Advanced Programmable Interrupt Controler. It basically handles interrupts and multi-core functionality. Having the "nolapic" option enabled you basically limit yourself to a single core/CPU. Many people use it to bypass problems with their system hanging at boot (mostly due to Kernel Mode Setting problems, which can be a pain... :/ ).

Here's what you can do to test it out. When booting, in GRUB, before choosing an option to boot (or letting GRUB do that for you after the 5 seconds timeout), select the option you want to boot (most probably the first on the list) and press the "e" key. Find the line that ends with "ro nolapic splash" (you'll probably need to scroll a bit) and remove the "nolapic" part. After that press F10 to boot the edited config. If the system boots without problems, check if you have all your cores visible and active. If so, then we'll make this setup permanent in the next posts (don't have my Sparky environment with me right now and I don't want to advise on such things out of my head - too risky ;) ).