I am having an issue with how ESXi handles IPMI. The system process' vmklinux_9:ipmi_thread constantly utilizes a full CPU core. This bug seems to have been fixed in ESXi 5.5U1 (KB 2065824, PR 1075046). However, it now happens for me on version 6.0 build 3247720. As a workaround I tried disabling IPMI (setting VMkernel.boot.ipmiEnabled to false), yet after a reboot IPMI is still used for some reason. Motherboard and IPMI controller BIOS/firmware are latest versions.