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by bayindirh 687 days ago
> I guess by queue he meant the processor internal work queue...

Yes, I meant the internal one. Also, when you enable SMT, a small tag is added in front of every instruction, noting which logical core owns this instruction for a given physical core. So instead of tagging every instruction with a core-ID, you add a longer tag in the form of core-ID/logical_core-ID.

This extra tagging also makes instructions bigger, so the queue can hold less instructions, adding fuel to already chaotic and choked FPU logistics.

As a result, if you're saturating your FPU(s), SMT can't save you. In fact can make you slower.