VMware vSphere 7.0 and ESXi 7.0 raised the requirements when it comes to CPU and CPU compatibility. As with any major version of ESXi, there are new CPUs that are supported as well as old CPUs that are reaching the end of support.

This basically means that if you have an older system that has an older CPU, you should check whether this system will be supported with ESXi 7.0. Today's article is focused on vSphere 7.0 and unsupported CPUs.

Before upgrading your ESXi to 7.0, you have to upgrade your vCenter Server. Here is our detailed article: How to Upgrade to vCenter 7.0

When you try to install ESXi 7.0 on a server with an unsupported CPU, you'll see a message like this.

VMware ESXi unsupported CPU message

VMware ESXi unsupported CPU message

However, there is also a workaround that allows you to bypass the ESXi unsupported CPU check. We'll talk about this later because the workaround is unsupported by VMware.

ESXi 7.0 hardware requirements

  • CPU details: VMware ESXi0 basically needs a CPU with at least two CPU cores, which is the majority of CPUs today.
  • BIOS Settings: NX/XD bit to be enabled for the CPU in the BIOS.
  • 4 Gb of RAM: This is the bare minimum, but as virtualization needs memory for your VMs, the more you have, the better.
  • Modern Guest OS: If you want to run 64-bit VMs, you'll need support for Intel VT-x or AMD RVI, which must be enabled on x64 CPUs within the BIOS.
  • Boot Device: 8 GB for USB or SD devices, and 32 GB for other device types such as HDD, SSD, or NVMe.
  • Storage: SCSI, SATA via supported storage controller.

Note: Due to changes in the partitioning scheme, you can no longer revert to the previous version of ESXi (via SHIFT-R). This was always the case with VMware ESXi; however, now, you'd have to create a backup of the boot device before the upgrade.

ESXi 7.0 unsupported CPUs

There are two family models that are no longer compatible and won't work under ESXi 7.0. Those CPUs were basically made during the 2010 era, so it's about time for them to retire.

  • Intel Family 6, Model = 2C (Westmere-EP)
  • Intel Family 6, Model = 2F (Westmere-EX)

The Westmere-EP architecture was based on two- to six-core CPUs, while Westmere-EX was a ten-core CPU model. This was Intel's CPU architecture right after Nehalem (my first lab). It was about 10 years ago, yes.

Now you might wonder how to easily check whether the CPU is compatible and supported or not.

Check the CPU model in the VMware Compatibility Guide

You can check the CPU by going to the compatibility page at VMware.

From the list selection, you can select the ESXi model and CPU series. Then hit the Update and View Results button.

Select ESXi 7.0 and your CPU model

Select ESXi 7.0 and your CPU model

The page will refresh and show you the results of the server model with the CPU and supported ESXi 7.0 version.

If you don't see any results, your CPU is not supported. Try with a newer CPU if you think you're having issues.

Server device and model information

Server device and model information


Are there workarounds? Yes, of course. The first is advice to someone who is looking to run VMware virtualization software on older hardware. If your hardware is 4–5 years old, you might hit the limit of compatibility (or you will soon), but for now, you should still be able to run ESXi 7.0.

If your system is not listed on the VMware compatibility page, you can still run your ESXi 7.0 on it, but don't expect Support to help you out if you hit some hard problem.

You can still run some less critical production workloads or your company monitoring solution on that hardware, but most likely, you'd want to sell this hardware and purchase newer equipment.

If you still want to run an ESXi 7.0 and you know that your CPU is not supported and your installation gets you to the page with an error message, there is a solution.

Disclaimer: Note that I have not personally tested this solution as I don't have an old CPU to perform the tests. The solution was described in VMware forums and on a few blogs. So, take it or leave it.

You'll have to be directly at the server console or remotely via ILO, DRAC, or IPMI. When you run the installer, use this shortcut:

Shift + O

(Note: this is the letter "O," not the zero "0").

Enter Shift plus O

Enter Shift plus O

That changes the screen to the one below and allows you to enter a special parameter that enables you to bypass the validation during the installation/upgrade.

Allow Legacy CPU value

Allow Legacy CPU value

Remember that this is not supported by VMware.

Note that the parameter you entered to bypass the installer will be lost after reboot. If you want to keep this value, you have to edit the boot.cfg file, which is located on the media you're booting from. You may be booting from a local SATA drive, USB stick, or other media, so it depends on your configuration.

Basically, you have to edit the boot.cfg file located in two places on the boot media. You can find this file in /bootbank/boot.cfg and in /altbootbank/boot.cfg.

There is a "kernelopt" section where you can append this parameter.

Allow Legacy CPU via SSH

Allow Legacy CPU via SSH

This is not advice to proceed or not to proceed. It's a tip, and you can use it if you want. Personally, as I said, I would not use it to "force" a run on a production system, but this can be a perfect fit on test or home lab systems that still work and that can be used for learning or running test scenarios.

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As you can see, checking the hardware for compatibility on the VMware site isn't difficult. It might also be interesting to check for network interface cards (NICs), as with ESXi 7.0, many legacy Linux drivers have been phased out. As those drivers were necessary to run, for example, many Realtek-based NICs, it seems those will no longer work under ESXi 7.0. But you can still upgrade your NICs to supported ones or seek another workaround if there is one. Good luck.


  1. michiel breur 3 years ago

    Keep in mind you need to put AllowLegacyCpu=true behind the line that's already there when installing.  

    Also there's no need to edit any files it will just work afterwards. 

    I'm more interested in a way to update by bypassing the 'image is not supported' message. 

  2. Allen 3 years ago

    I have a AMD Ryzen 2700 , no problems. Esxi 7.0

    • Leos Marek (Rank 4) 3 years ago


      I run vSphere on 7 years old DELL Optiplex with i5 CPU. The fact that it runs well does not mean that its supported by VMware. I guess this was the main idea in this post.


      • Leos Marek (Rank 4) 3 years ago

        Sorry, I did not express correctly. I run vSphere 7 on 7 years old desktop PC .)

        • enjang 3 years ago

          What i5 series you use? 
          I have i5-4200M and i5-3320M. 

  3. Magnus Brynhagen 3 years ago


    Ihave an old DL380G7 with 2×5650, I just did the Shift+O "allow legacy cpu" once during install, no files edited.

    It installs and works fine, next problem is patch updating, vCenter won't do it cuz of incompatible CPU.

    Anyone have any trix to "force" an update or maybe a hack or patch or whatever?  

  4. Chris 3 years ago

    This workaround doesn't seem to be working for me. I have an older Intel S5000PS board with dual quad core X5365 CPU's. When I boot with the allowLegacyCPU=true option, it still fails the CPU check during the ESXi install routine. I noticed in the image shared above that the boot options for "runweasel" and I think it was "boot cdrom" (or something to that effect) were not present. Do we replace these options after shift-o with just the allowLegacyCPU=true? Seems if this is the case, the installer will not continue.

  5. Marco86 3 years ago

    I have been skilled to setup an esxi on chinese motherboard but i have two problems:
    I can’t find nx bit on bios setup and vmci on web interfacce during setup of VM doesn’t start.
    It seems VM start but when I clic play on picture after 3/4 second it shutdown.
    There is an error on vmware.log about “mks: panic… signal 4”

    My mother board + CPU: x89 motherboard, socket G34, amo opteron 6172

    • Aran Kaspar 2 years ago

      Did you get it working on the opteron 6178? I have a pair of 6128's and it completes progress bar but is stuck on a black screen with little text.

      Just says Shutting down firmware services… Relocating module and starting up kernel… 

      I cleared out the cdrom boot easyweasel line and only put the allowLegacy….yatayata. 

      I bought two 6380's because my board "supports them" after latest bios flash but they wouldn't POST.

      • aran kaspar 2 years ago

        I didn't add it at the end of the existing entries. After adding allowlegacyCPU=ture at the end of cdrom runweasel allowLegacyCPU=TRUE 

        it works.

        Except, when I run a linux VM it doesn't allow me to use the vmware console. 

        Every time I click on the console it shuts off the VM. Web or VMRC.



  6. Sameen 2 years ago

    dear one problem that I faced is I cannot find storage while installation…..can anybody help me in this regard……..Remember it is detecting USB but it is not detecting Raid Storage

  7. Sameen 2 years ago

    Is there any possibility to install Esxi 7.0 with unsupported CPU?? i have tried below mentioned link but the issue is i am unable to get storage where i want to install. It shows only USB which contains ISO of Esxi

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