Intel Core i7-4770K Review: Haswell Has Landed

Haswell Microarchitecture - FIVR

There's little question that current-generation microprocessors from Intel (and others) are complex designs that require highly-tuned, well-regulated power supplies of various voltages for multiple component blocks, along with both active and idle or standby power states. CPU cores, graphics cores, the DDR memory interface and PCI Express lanes, all need their own power planes, many of which are required to dynamically scale with varying workloads. 

Within the Haswell architecture, Intel's 22nm 3D Tri-Gate 3D transistor technology certainly helps drive lower power consumption in general but Haswell also has a few other tricks up it sleeve to further reduce power consumption. Specifically, Haswell is the first X86 processor to incorporate on-die voltage regulators, which in turn allows the chip to reduce the number of VREG inputs from five to one simple input.

In this simplified block diagram, Intel is showing Haswell's new FIVR, or Full Integrated Voltage Regulator, technology.  As it's shown here, Processor, Graphics, System Agent, IO and PLL (Phase Lock Loop / Clock) Voltage Regulators are now combined into a single input VR.  Intel has kept its DDR memory VREG discrete, so it can migrate with industry standard changes as needed.  Regardless, at a high level, Haswell's new FIVR power design allows for a dramatic reduction of complexity in motherboard design.  All those Voltage Regulator Modules are now on-chip. However, the intrinsic benefits of an integrated Voltage Regulator design go far beyond just board real estate savings. 

Haswell's integrated Voltage Regulator design also allows the chip to ramp voltages faster -- about 5X to 10X faster than the previous generation's external VR design.  Haswell's FIVR array actually operates at 125MHz.  As a result, Haswell is able to enter deeper sleep states and come out of those sleeps states more quickly.  This may not result in as dramatic a power consumption on the desktop but Intel is claiming up to 50 percent longer battery life for Haswell notebooks, versus the previous generation of Ivy Bridge machines.

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