The new deepest sleep state, called C7 will be able to reduce the power consumption of the CPU to only 0.05A (0.6W). As this occurs in the deep sleep state, when most other 12V devices are either in low-power states or turned off, this can reduce the 12V load on the power supply significantly. For some power supplies this low load can cause voltage regulation issues, if combined with high loads on the minor rails (3.3V and 5V).
|PSU Family||Model||Haswell C6/C7 Compatibility|
|Newton R3||1000W||Yes, compatible|
|1000W White||Yes, compatible|
|Tesla R2||1000W||Yes, compatible|
|650W White||Yes, compatible|
|Integra R2||750W||Likely compatible|
Newton R3 and Tesla R2 testing:
The Newton R3 and Tesla R2 use the DC-DC method for generating the 3.3V and 5V rails. All power supplies that use the DC-DC method are able to output their full 3.3V/5V ratings even with no load on the 12V rail, so Tesla R2 and Newton R3 power supplies will easily support the new sleep states introduced with Intel’s Haswell platform.
Integra R2 testing:
While Intel has not yet released their testing methodology or a formal definition of Haswell compatibility, we have performed extensive tests with Integra R2 PSUs. The Integra R2 uses the group regulation method for generating the 3.3V and 5V rails, which means output voltages will be affected by a large imbalance between the load on those rails and the load on the 12V rail.
Current-generation group regulated power supplies are much more stable in this regard than power supply platforms designed a few years ago, and the Integra R2 units will provide voltages within ATX specification for any load levels on 3.3V and 5V likely to occur during system sleep.