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I do understand that there are quite few articles around talking about how to enable multiple cores. But I did encounter few issues when I tried to do it by myself. Therefore, I write this down just as reference.

Why do we need to have Multiple cores in your VM?

The reason is simple. Microsoft Windows only support limited number of processors on their OS.

 

Win OS Version Max Processor
Win2k3/2k8 Standard 4 CPUs
Win2k3/2k8 Enterprise 8 CPUs
Windows 2003 DataCen 32bit 32 CPUs
Windows 2003 DataCen 64bit 64 CPUs
Windows 2008 DataCen 64bit 64 CPUs
Win 2k8 R2 64 physical CPU or 256 logical CPU

 

Let’s say, if you are running a Dynamics AX AOS server, it is required to run multiple cores to do your batch jobs. With AOS server, you can setup number of helpers to work with distributed batch jobs. The maximum number of helpers (number of supporting cores) is 21. If I run AOS on Windows 2003 Standard, I need to enable multicores so a Win2k3 standard can run 8 cores to help me improve calculating.

How do we enable multicore on VM?

You need to do that in vm 7 hardware which means it should be vSphere 4.x version. (I was told it could work on ESX 3.5, but I haven’t tried yet). Most important and difficult condition is you need a Enterprise Plus license to let VM to support 8 vCPUs.

You can work around by installing a new ESXi host(not your vCenter since CPU license is related to Host license)

Let’s say if  you want to have your vm to have 4 vCPUs and 2 cores on each vCPU. Here is a trick. You need to give this VM 8 vCPUs(4vCPU x 2 cores= 8vCPUs) instead of 4 vCPUs.

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This will give VM 8 vCPU all together. Now you need to setup 2 cores for each vCPU. In terms of doing that, we need to add a special Configuration Parameters. Turn off you VM->Edit VM Setting

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Manually add this new row into your sheet.

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Then, you turn on VM.

How to verify I’m using multicores?

Well, the basic way is to open Task Manager and Device Manager.

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Please be notice that the above picture is from another example. It should show up with 8 cores but it only shows 4 cores because that’s another machine. I will replace picture later.

There is another way to see number of cores if you running windows 2008 above.

Get into your machine->cmd->wmic->cpu

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Move your scroll bar to middle. Here is just example. Again, it’s not related to my test machine. And you need to remember this method only works on Win2k8. For W2k3, you need other third party tools.

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Possible problems you may run into

Like what I said before, you need to have Enterprise Plus license or Evaluation license on host. Otherwise, you will be pleasure to see this error.

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What difference between multicores and multiCPUs?

The answer is, from performance wise, nothing. It’s just different way to call it. VM still pass on the CPU cycle to host and process it. The best practise is if you want to have 8 vCPU, you can either have 4 vCPU x 2 cores or 2 vCPU x 4 cores.

It’s total you choose and your call.

 

Reference:

Vmware KB Article: 1010184

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