Rules for specifying CPU options for an Amazon EC2 instance - Amazon Elastic Compute Cloud
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Rules for specifying CPU options for an Amazon EC2 instance

To specify the CPU options for your instance, be aware of the following rules:

  • You can't specify CPU options for bare metal instances.

  • You can specify CPU options both during and after instance launch.

  • To configure CPU options, you must specify both the number of CPU cores and threads per core in the request. For example requests, see Specify CPU options for an Amazon EC2 instance.

  • The number of vCPUs for the instance is the number of CPU cores multiplied by the threads per core. To specify a custom number of vCPUs, you must specify a valid number of CPU cores and threads per core for the instance type. You cannot exceed the default number of vCPUs for the instance. For more information, see Supported CPU options for Amazon EC2 instance types.

  • To disable simultaneous multithreading (SMT), also referred to as hyper-threading, specify one thread per core.

  • In the console, when you change the instance type of an existing instance, Amazon EC2 applies the CPU option settings from the existing instance to the new instance, if possible. If the new instance type doesn't support those settings, the CPU options are reset to Use default CPU options. This option uses the default number of vCPUs for the new instance type.

    To update settings for the new instance, select Specify CPU options under Advanced details in the Change instance type view.

  • The specified CPU options persist after you stop, start, or reboot an instance.

  • If you use Reserved Instances, discounts may not be applied when you configure Optimize CPUs for instances launched from license-included Windows AMIs in the same payer account. We recommend that you use Savings Plans to reduce vCPU-based licensing costs and provide comparable savings on your compute costs.

  • To save on licensing costs for instances launched from Windows and SQL Server license-included AMIs, you must configure a minimum of four vCPUs. If you configure fewer than four vCPUs, default billing is applied.

  • Optimize CPUs for License-Included instances is not supported on T3 instance types.