Vmware Esxi 5.5 Requirements -

The NX/XD bit must be enabled for the CPU in the BIOS. 2. Memory (RAM) Requirements

At least one Gigabit or faster Ethernet controller is required. vmware esxi 5.5 requirements

4 GB of physical RAM is required to run the installer. The NX/XD bit must be enabled for the CPU in the BIOS

The following software requirements must be met: vmware esxi 5.5 requirements

If you are scaling up, these are the maximum limits for a single ESXi 5.5 host:

It is impossible to review the requirements without mentioning the lifecycle status.