White Paper - Power Management in Intel Architecture Servers
In the example shown, when all four cores are fully utilized no
headroom remains, but if two cores are idle their power consumption
will also be lower because the frequency will drop to a lower operating
point, assuming DBS was turned ON. The remaining two cores can
operate at a higher-than-rated frequency until the overall package-
level thermal and power limits are reached. Similarly, if three cores are
inactive, the remaining core can run at a still higher frequency.
Note that there is only one turbo state frequency defined, but its
value depends on how many cores are active. With more inactive cores,
the turbo frequency of the remaining active cores is higher, while
maintaining the overall package within its power and thermal limits.
There is also a mode, called the enhanced legacy turbo mode, in
which all the cores are working but not at their full capacity, as shown
at the bottom right of Figure 4. In this case the core frequency
can be increased until the thermal package limit is reached. In all
circumstances, the package always stays within its thermal limits.
A Test Case for Turbo Mode
In the first scenario, the user can use the Advanced Configuration and
Power Interface (ACPI) dump utility to check the number of P-states
published by BIOS when turbo mode is enabled. The system will have
one extra P-state when turbo mode is enabled.
For example if a processor is marked with frequency 2 at .6 GHz,
the BIOS will publish three P-states (P2–2.4, P1–2.5, P0–2.6) with
turbo mode disabled; when turbo mode is enabled BIOS will publish
(P3–2.4, P2–2.5, P1–2.6, P0–2.67).
Intel® Turbo Boost Technology
No Turbo
Turbo Mode
OR
Active cores running
workloads < TDP
Workload Lightly
Theaded or < TDP
Core 0
Core 1
Core 2
Core 3
Frequency (F) Frequency (F)
Core 0
Core 1
Core 0
Core 1
Core 2
Core 3
Frequency (F)
Figure 4. Turbo mode uses the available headroom in processor package power limits�
P-states Without
Turbo Mode
P0 2�6 GHz
P1 2�5 GHz
P2 2�4 GHz
P-states With
Turbo Mode
P0 2�67–2�8 GHz
P1 2�6 GHz
P2 2�5 GHz
P3 2�4 GHz
6
White Paper: Power Management in Intel® Architecture Servers