4 ms·
But clock speed doesn't really mean anything these days either. 1Ghz is just as arbitrary - the instruction rate through two CPUs at the same clock rate can var
by cbzoiav 8y ago
But clock speed doesn't really mean anything these days either. 1Ghz is just as arbitrary - the instruction rate through two CPUs at the same clock rate can vary massively.
So a vCPU is an arbitrary unit but as each is equivalent then they can be benchmarked for the relevant workload.
- BeeOnRope 8y agovCPUs are not at all equivalent across instance types! One vCPU is a single hardware thread on an actual core (ie, two vCPUs is a full core of whatever the underlying machine is if it is an SMT2 core). So the power of a vCPU is quite different across different hardware types. You might be thinking of ECU (EC2 compute unit), which are intended to be comparable across hardware and are normalized to some old 1.7 GHz CPU that I guess was common in the early days of EC2. Amazon doesn't promote the ECU rating for instance types much, but it's still available if you look.
- tptacek 8y agoJust to clarify, if you read below, you'll find that vCPUs on the A1 instances are each physical ARM cores.
- BeeOnRope 8y agoRight, I didn't mean to imply otherwise - but I can see how what I wrote could come off that way. One vCPU is a single hardware thread, which means that on cores without SMT, one vCPU == one core. Since the A72 doesn't have SMT, you get one core per vCPU. So in that sense, you are getting more bang for your buck if you just count physical cores: twice as many cores per vCPU... FWIW, I tried to look up the ECU rating of the new ARM instances but they are listed as "NA" in the EC2 console.