Fourth generation Intel Core preview: all about Haswell

Preview of Intel's fourth generation Core processors


Power management

The new generation processors will also be more energy-efficient. On the previous page we described how the voltage and clock frequency of the ringbus and L3-cache are independent of the cores in Haswell. With Sandy and Ivy Bridge it was already possible to independently increase or decrease the clock frequency of the GPU. Because the Haswell chip has effectively been split into three almost independent parts, it makes much more accurate power management possible.

Intel claims it has implemented minor and major improvements in terms of energy efficiency all over the place. Haswell processors should be more efficient than its predecessors on all performance levels. Intel also made the link between the CPU and chipset (PCH) more efficient, and the chipsets will support very energy-efficient interfaces from the world of smartphones and tablets. It's possible to connect sensor chips to busses such as I2C and SDIO which makes the link more economical than USB. The controllers for USB, SATA and PCI-Express have also been overhauled to improve efficiency.

The main improvement in the area of energy-efficiency is the so-called S0ix state of the processor. This makes the operating systems think that the processor is active, while in fact most of it is inactive. The active parts ensure that the processor can be ready in a matter of milliseconds. The new S0ix mode makes the Haswell processor up to 20 times more efficient in idle mode than Sandy Bridge. Last year Intel claimed a Haswell laptop would be able to be in "connected standby" for more than 10 days, a mode with a semi-constant internet connection for synchronising data. It's this S0ix mode that will make that possible. Since this mode is transparent for the OS, nothing has to be changed in it for it to be able to take advantage of the lower idle consumption.

A new C7 power mode almost completely disable the processor, while the graphics card remains on. This is useful for when you're reading a web page, or giving a PowerPoint presentation. Right now processors are running at full power, but with Haswell they can largely be inactive.

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