This message was posted on behalf of Intel Corporation
Your particular Intel(R) Xeon processor does not have C3 Sleep mode, which is useful on laptops or when you computer/server is not going to run for long periods of time. Idle States (C-states) are used to save power when the processor is idle. C0 is the operational state, meaning that the CPU is doing useful work. C1 is the first idle state, C2 the second, and so on, where more power saving actions are taken for numerically higher C-states.