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layoric | 4 months ago

I must be confused, my understanding was m7a was 4th generation Epyc (Genoa, Bergamo and Siena) which I believe all have 2 threads per core no?

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electroly|4 months ago

You're not confused--AWS either gets custom chips without it, or they disable the SMT. I'm not sure which. Here's where AWS talks about it: https://aws.amazon.com/ec2/instance-types/m7a/

> One of the major differences between M7a instances and the previous generations of instances, such as M6a instances, is their vCPU to physical processor core mapping. Every vCPU on a M7a instance is a physical CPU core. This means there is no Simultaneous Multi-Threading (SMT). By contrast, every vCPU on prior generations such as M6a instances is a thread of a CPU core.

My wild guess is they're disabling it. For Intel instance families they loudly praise their custom Intel processors, but this page does not contain the word "custom" anywhere.