It looks like some things are not in sync.
The VMware Compatibility Guide for CPUs
still shows Intel Xeon 54xx when you select ESXi 6.5, All CPUs, Penryn for enhanced vMotion and Fault Tolerant sets.
However, Intel Xeon 5450 is also listed as "End of life"; although not "End of interactive support" in the Intel ARK website.
Technical thing to note is that Xeon 5450 is also shown as "No" for EPT. As far as I know, EPT is only required when nested virtualisation is in the picture. Not aware whether EPT is required for ESXi 6.5 itself. As I understand, EPT does give performance advantages even for regular VMs without nesting.
Thanks for your answer. I'll try again the update.
I have successfully upgraded my DELL Precision T7400N Workstation using 2 Intel XEON X5450 Quad Core Processors From VMWare EXSI 6.0 to VMWare EXSI 6.5.0 update 02 (or as it is called now VMware vSphere Hypervisor 6.5.0 Update 2). The only warning I received was that the mentioned Intel Xeon X5450 Processors may not be compatible with the next version of the EXSI Software and to plan accordingly. Which unfortunately was true, when I had originally tried to upgraded my VMWare EXSI software from 6.0 to 6.7 It stopped halfway through the loading process with a black screen and stated there was a compatibility error with the X5450 processor and to check the compatibility guide and went no further. So wrapping this up if your Using a Server/Workstation with an Intel XEON X5450 processor the latest and great version of the VMWare EXSI software that will work with this processor is the 6.5.0 update 02 (or as it is called now VMware vSphere Hypervisor 6.5.0 Update 2).