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We have a IBM idataplex blade system, it has two sockets and one of the socket is having hexacore intel chip and running Centos OS 5.x 64bit. I would like to know, whether it is required to re-install the operating system upon addition of another processor in the other socket. Or the OS which is already installed will identify the second processor.

Thank you, AVP

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migrated from Jun 11 '12 at 9:39

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As per answers already provided, you shouldn't need to do anything (uname -a should report a kernel version including the string 'smp'). You should enable and configure irqbalance of it's not already running. – symcbean Jun 11 '12 at 10:00

No, it is not needed.

The only modern OS that I am aware of that needs a reinstall to use multiple cores is NT/XP on a single socket, single core host.

GNU/Linux systems did not ever need this; unless running a kernel specifically without SMP. And that is extremely unlikely since uou would have used only one core of your old hexacore chip.

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But even when you ahve installed a non-SMP kernel you wouldn't have to reinstall. You would have to install a new SMP-kernel to start using the additional CPU but that's still not as drastic as reinstalling the entire OS. And just to be complete: RHEL and it's derivatives allow hot-adding and removing RAM and CPU. I've seen that done on a virtual system and if the hardware supports it that should be possible to (with an SMP kernel off course). – Bram Jun 11 '12 at 10:23

As others have mentioned you won't need to do anything from the operating system side of things but given this system is almost certainly NUMA-based one using recent Intel Xeon's then you will have to balance out your memory between sockets or add new memory to the second socket's memory DIMM slots.

You'll need to either read your model's memory load-out documentation or provide us with exact details of the model and existing memory load-out of the box as it is now.

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Obviously, your OS installation must already support multiple cores. So no, there's nothing you need to do. The core count will just go from 6 to 12. The physical sockets don't particularly matter to the OS.

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All recent Linux Kernels are SMP kernels, you will be able to add CPU units without reconfiguring/reinstalling any thing.

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