Recently VMware released ESXi 7.0 and finally deprecated support for 1st generation Intel CPUs (Westmere). This is bad news for our lab environments, although they are 10 year old CPUs so we can’t be too upset. Never fear there is now a boot option that allows you to bypass the unsupported CPU check during the install or upgrade process.
1. As ESXi is booting press SHIFT + O and append:
This will boot the installer bypassing the CPU check.
2. If installing on a USB drive, post install you will need to edit the boot.cfg and append the above string the the kernelopt line.
More information located on VMwares website here.