DIPM should be enabled on Haswell ULV systems...

[siya-u]

I'm using a T440s, which has Core i5 i4300 ULV processor. The system had a 500 GB HDD then I've upgraded with an Intel 330 SSD. I installed Intel SSD Toolbox and the software warned me that DIPM setting was disabled and should be enabled for optimum power savings. I then enabled the setting via SSD Toolbox and experienced a 5 degC reduction in idle processor temps.

It was strange, and I begun to search for more info on the situation. Then I found an article, written by SiSoftare (the producers of Sandra system info. software), which states that on Haswell ULV systems, DIPM setting is vital for optimum power savings. Because of the integrated arcthitecture of Haswell ULV chip (basically, it is a SoC, System on a Chip, which integrates not only the GPU and memory controller, but also the south bridge, SATA and I/O connectivity, into the processor core), the processor can not enter low power C6, C7 states if the SATA interface cannot be put into power savings mode. To do this, DIPM (Device Initiated Power Management) setting should be enabled but it is not easy to do this on Windows 7 and 8 because the setting is hidden by default.

This is the article which gives detailed info on the subject; they also performed idle/load power consumption and battery life tests:

Fix: Intel Gen 4 (Haswell ULV) requires DIPM for low power and is crippled without it

If your are using an Intel branded SSD, DIPM setting can easily be enabled via SSD Toolbox software. Unfortunetely, there is not an easy option or a software for other vendors which enables DIPM setting. You should modify the registry to unhide DIPM setting under Control Panel - Power. And here is how to:

AHCI Link Power Management - Enable HIPM and DIPM

You should also be using AHCI mode and approprite AHCI drivers. Using DIPM helps both CPU idle temps reduction and further power savings, thus providing more battery life and a cooler system.