Intel Core i7-4770K

The quad-core Intel Core i7-4770K is the company's new top-end chip based on its Haswell microarchitecture and its second processor built on the 22nm process node. The chip includes a number of new capabilities and enhancements and is a notable step forward in CPU efficiency, but enthusiasts may be disappointed by its lower overclocking potential.

The Haswell microarchitecture is a "tock" in the company's tick-tock model of development. In Intel's nomenclature, "ticks" are used for smaller process technologies and the introduction of new manufacturing techniques, while "tocks" are reserved for core architectural improvements that change the CPUs feature sets and capabilities. Last year, Ivy Bridge debuted as the first 22nm processor manufactured on Intel's FinFET technology. This year, Haswell introduces a number of changes to the underlying CPU structure.

The chip we're reviewing today is the Intel Core i7-4770K. It's a 3.5GHz chip with a 3.9GHz Turbo speed (identical to the Ivy Bridge Intel Core i7-3770K) and formal support for up to DDR3-1600. The CPU's TDP has increased somewhat compared with the 3770K, from 77W up to 84W. This likely reflects changes to the integrated voltage module, and the fact that the VRM's power consumption must now be dissipated by the CPU heat sink.

The "K" in the Core i7-4770K denotes that this chip has a 3.5GHz base speed rather than the 3.4GHz base clock of the vanilla Core i7-4700. It also features an unlocked clock multiplier, which makes it easier to overclock. The lure of higher clock speeds comes at a price?not only is the Core i7-4770K $30 more expensive than the 4770, it lacks support for Intel's various hardware virtualization technologies (v-Pro, Vt-d) and Trusted Execution Technology (TXT).

It's also missing the new Transactional Synchronization Extensions (TSX), which is unfortunate. TSX is a new feature, introduced in other Haswell chips, that offers programmers a more efficient way to manage certain multi-threading performance problems. It's not a feature that we expect to make much difference in the short run, but long term, the capability could be vital to improving multi-core scaling.

The Haswell features and enhancements that apply to all CPUs, including the 4770K, are as follows:

AVX2 (Advanced Vector eXtensions 2): This new instruction set builds on AVX and extends the size of the AVX registers to 256 bits, from 128. This allows the chip to perform a larger calculation in a single cycle, rather than two. AVX2 also includes new efficiency-boosting instructions and adds support for FMA3 (Fused Multiply-Add). That's an instruction that AMD added with its Piledriver CPU in 2012?adding it to Haswell will boost overall adoption.

More Scheduling/Execution Resources: Haswell has more integer and AVX registers compared to Ivy Bridge, and the AVX registers (168 of them, up from 144 in IVB) are all 256-bit. The chip's maximum throughput has also been increased, thanks to the addition of new integer and memory ports. Peak floating point instruction throughput has doubled, to 32 FLOPs per clock per core, up from 16 (single-precision), and 16 double-precision FLOPs per core, up from eight.

Higher Internal Bandwidth: Adding additional execution capabilities isn't useful if you don't beef up the chip's internal structures to support them. This is an area where Intel has gone all out?L1 cache read/write bandwidth has increased doubled compared to Ivy Bridge, as has L2 bandwidth.

Alongside these changes, Intel has moved the voltage regulator for the CPU from the motherboard to the processor. This is a significant change as far as total power consumption is concerned, but the impact is going to be confined to the mobile space. Moving the VRM (Intel calls the new design a Fully Integrated Voltage Regulator, or FIVR) on-die allows Intel to control CPU power consumption much more quickly and reduce power consumption more effectively.

This, however, is an advantage we expect to see mostly in the mobile space. There's a downside to moving the voltage regulator aboard the CPU?the voltage regulator generates a fairly significant amount of heat, and there's only so much room under the heat spreader (or shim) for dissipating it. Given that CPU power consumption rises as temperatures increase, the onboard VRM has the potential to increase CPU temperatures and power consumption at the high end, while simultaneously improving mobile performance by allowing for fine-grained clock gating. Based on our desktop tests, that's what's happened.

One caveat: Our benchmark tests contain no integrated graphics tests. Problems with our motherboard prevented us from testing the new IGP in time for publication. According to Intel, the new integrated graphics solution for Haswell is 15% to 20% faster than the one for Ivy Bridge desktop CPU. Given that Haswell's integrated GPU contains 20 EUs (Execution Units), up from 16 in Ivy Bridge, that's in line with expectations. A 15% to 25% increase in GPU performance over Ivy Bridge isn't going to be enough to replace a dedicated video card for gaming enthusiasts, but it does represent a solid step forward for the architecture as a whole.

Source: http://feedproxy.google.com/~r/ziffdavis/pcmag/~3/rDMykyhBg5o/0,2817,2419798,00.asp

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