EPYC EVC Mode

[tman24]

I'm running the latest build of 6.5U1 on a dual socket EPYC 7351 system. ESXi installed fine, along with vCenter. Everything seems to be working ok, but when I try and enable EVC for AMD CPUs, Every option I select says the CPU isn't compatible, and based on VMware's documentation, there should also be a 'Zen' option of which on my system, there isn't. I've tried the 'Opteron Gen3 (without 3DNow)' that *should* also work, according to the docs, but that says the CPU is incompatible as well!

Anyone know what gives? 6.5U1 is meant to be fully comaptible with EPYC, so I'm now sure what's going on.

Thanks

[MohamadAlhousse]

Hi tman24​

Please check the below link. You should select "AMD Opetron" as an EVC mode.

VMware Compatibility Guide - System Search

Regards,

[tman24]

Thanks for the suggestion. I can confirm that if I try to set the EVC mode to anything other than 'Gen 3 without 3DNow!', I get the following error;

The host's CPU hardware does not support the cluster's current Enhanced vMotion Compatibility mode. The host CPU lacks features required by that mode.

If I try to set the EVC mode to 'Gen 3 without 3DNow!', I actually get a different error;

The host cannot be admitted to the cluster's current Enhanced vMotion Compatibility mode. Powered-on or suspended virtual machines on the host may be using CPU features hidden by that mode.

The only VM I've got running on the host at the moment is the vCenter Appliance, and I can't shut that down, or I won't be able to change the EVC mode! Only way I can see is if I migrate the appliance off the host, then try setting the EVC mode again when the appliance is running somewhere else. Will that work?

[MohamadAlhousse · Accepted solution]

Hi tman24​

Yes it should work dear. If you have a multi-host cluster just do the following to set the EVC mode as no running VMs should be running on the cluster.

1. Evict the host running the vCenter VM from the cluster and leave the other host(s) in the cluster. Don't shutdown the vCenter VM.

2. Set the EVC mode on the cluster level

3. Add the host back to that cluster.

Regards,

[tman24]

Thanks for your help. The key was to move the vCenter Appliance off the host and with no other running VM's, I could then change the EVC mode the 'AMD Opteron Gen 3 without 3DNow!', the move the vCenter appliance back. No other way I could see.

I still don't know where the 'AMD Zen Generation' EVC mode is, unless it's not actually in the vSphere yet.. It seems strange that for a brand new CPU you have to use a pretty old EVC mode.

[tman24]

Sorry to follow up on this.

While I've now got the AMD Opteron Gen 3 without 3DNow EVC mode active, it's become pretty obvious very quickly that this mode doesn't expose the AVX/AVX2 CPU features to guests. AVX was introduced in AMD Opteron Gen 4, but that mode doesn't work with EPYC.

I keep seeing mention of the 'AMD Zen Generation' EVC mode, and VMware's CPU compatability guide shows this as a feature of 6.5U1, but it's definately not there in my list in vCenter. There's little info out there on this, but I'm confused to why a brand new CPU has to use a very old EVC mode, and isn't even compatible with later Steamroller or Piledriver AMD CPU EVC modes.

Just where is the  Zen Generation EVC mode!

[VMAdmin0]

Looking for the same answer here. Is "AMD Zen Generation" EVC mode going to be made available in vCenter version 6.5?

Here's the link to the above EVC mode listed on VMware pages:

VMware Compatibility Guide - cpu

[bob_struck]

I know this is really old.  When you say "Evict" do you mean just a right click disconnect?  Set it on the cluster, then connect it back?