Rules for specifying CPU options - Amazon Elastic Compute Cloud
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Rules for specifying CPU options

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

  • CPU options can only be specified during instance launch and cannot be modified after launch.

  • When you launch an instance, you must specify both the number of CPU cores and threads per core in the request. For example requests, see Specify CPU options for your 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 CPU cores and threads per CPU core per instance type.

  • To disable multithreading, specify one thread per core.

  • When you change the instance type of an existing instance, the CPU options automatically change to the default CPU options for the new instance type.

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