User Manual

Intel
®
Xeon
®
Processor 5600 Series Datasheet Volume 1 149
Thermal Specifications
The T-state control word is defined as follows:
7.3.2.6.10 Energy Accumulator Read
Intel Xeon processor 5600 series energy consumption may be monitored with regular
reads of the free running Energy Accumulator. The Energy Accumulator reports
processor energy consumed on the VCC, VTT, VCCPLL and VDD power rails in Joules in
an unsigned, 32-bit fixed point binary format. The least-significant 16 bits report the
fractional data and the most significant 16 bits report the integer data. Because the
Energy Accumulator is constantly incrementing, the data is only relevant as a delta
between two subsequent reads.
Overflow in the accumulator is infrequent, but it will occur constantly during normal
execution. Therefore, the PECI host controller or firmware must be designed such that
it can guarantee a polling rate sufficient to prevent aliasing. Recommended polling
rates are between 1Hz and 10Hz. As an example, a processor steadily consuming 130
W of power will overflow the accumulator once every 8.4 minutes.
The free running nature of the PECI Energy Accumulator register allows for irregular
timing on reads. It is expected that the PECI host controller or firmware will manage its
own time stamps.
Accuracy of the Energy Accumulator may be processor or platform specific, and is a
function of the Voltage Regulator IMON solution.
On processor power-up, the Energy Accumulator Register is reset to 0x0. On all
subsequent processor resets where power is maintained to processor, the accumulator
continues to count uninterrupted.
The Energy Accumulator register is defined as follows:
0x4 50% clocks on / 50% clocks off
0x5 62.5% clocks on / 37.5% clocks off
0x6 75% clocks on / 25% clocks off
0x7 87.5% clocks on / 12.5% clocks off
Duty Cycle Code Definition
Figure 7-26. ACPI T-State Throttling Control Read / Write Definition