CPU options for Amazon EC2 instances
Many Amazon EC2 instances support simultaneous multithreading (SMT), which enables multiple
threads to run concurrently on a single CPU core. Each thread is represented as a virtual
CPU (vCPU) on the instance. An instance has a default number of CPU cores, which varies
according to instance type. For example, an m5.xlarge instance type has two CPU
cores and two threads per core by default—four vCPUs in total.
Note
You can't modify the number of threads per core for T2, C7a, M7a, R7a, and Apple silicon Mac instances, and instances based on the AWS Graviton processor.
In most cases, there is an Amazon EC2 instance type that has a combination of memory and number of vCPUs to suit your workloads. However, to optimize your instance for specific workloads or business needs, you can specify the following CPU options during and after instance launch:
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Number of CPU cores: You can customize the number of CPU cores for the instance. You might do this to potentially optimize the licensing costs of your software with an instance that has sufficient amounts of RAM for memory-intensive workloads but fewer CPU cores.
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Threads per core: You can disable SMT by specifying a single thread per CPU core. You might do this for certain workloads, such as high performance computing (HPC) workloads.
Pricing
There is no additional or reduced charge for specifying CPU options. You're charged the same as instances that are launched with the default CPU options.
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