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.
We tested the Core i7-4770K using Intel’s DZ87KLT-75K motherboard and 8GB of DDR3-2133 RAM in two DIMM slots. The Core i7-3770K was tested using the Intel DZ77GA-70K motherboard with the same RAM, at the same clock speed. An OCZ Vector 256GB SSD was used in both cases, as was an Nvidia GeForce GTX 680 discrete graphics card. All testing was done using a fully patched version of Windows 7 64-bit.Power was provided by a 1275W Thermaltake Toughpower 80 Plus Platinum power supply. We used the same stock Intel cooler on both chips to compare thermals in an apples-to-apples environment.
Different motherboards were necessary because Haswell uses Intel’s new LGA1150 design while Ivy Bridge and Sandy Bridge used the LGA1156 design. LGA1156 coolers will fit LGA1150 sockets—if you upgraded to Sandy Bridge several years ago and want to move to Haswell, you won’t need a new
CPU cooler to do it.
In our Adobe Photoshop CS6 test, the i7-4770K improved on the i7-3770K’s performance by 7.8%, completing our filter tests in 169 seconds, compared to 184 seconds for the Ivy Bridge processor. In Cinebench 11.5′s 3D rendering test, the benefit was similar—the 4770K turned in a score of 8.12, compared with 7.45 for the Ivy Bridge-based i7-3770K. Our POV-RAY 3.6 rendering test actually bucked this trend a bit—the 4770K’s rendering time in the program’s built-in benchmark was 193 seconds, compared to 233 seconds for Ivy Bridge. That’s a 17.2% reduction, and it shows that under the right circumstances, Haswell’s enhancements can pay substantial dividends.
Most of the improvements, however, smaller. Encode times in Handbrake 0.9.8 fell to 29 seconds from 31 seconds, (a 7.5% reduction). PCMark 7 performance jumped from 6,060 with the i7-3770K to 6,668 with the i7-4770K, an improvement of 10%. As AVX2 is adopted, the gap between Haswell and Ivy Bridge CPU performance will widen slightly, and while we don’t recommend buying a chip today based on what might happen in the future, it’s reasonable to think a further 6% to 10% performance delta will emerge in AVX2-friendly workloads.
Power consumption tests show that Haswell’s increased performance comes at the cost of some additional power. At idle, our GTX 680-equipped i7-3770K testbed [ok]drew 58W, while the same system equipped with the i7-4770K idled at 64W. While rendering in Cinebench, this increased to 113W for Ivy Bridge and 119W for Haswell. Under ten minutes using Prime 95′s Torture Test, the gap increased further, with the i7-3770K drawing 136W and the i7-4770K drawing 148W.
In and of itself, a 12W power difference isn’t much to sneeze at, but the two motherboards behaved rather differently under full load. The Core i7-3770K held itself at 3.7GHz, even as the maximum CPU temperature in Prime95 hit 90′C. Haswell, in contrast, backed off its “Turbo” clock—after 10 minutes of Prime95, the i7-4770K was running at just 85′C, but had reduced its own clock from 3.7GHz to 3.5GHz. This suggests that Intel’s automatic Turbo Mode controls are a bit more conservative on the DZ87KLT-75K than what the DZ77GA-70K motherboard used for Ivy Bridge.
If you do intend to overclock, don’t expect as much headroom from the process. According to multiple boutique PC manufacturers we spoke to, 4.4GHz to 4.5GHz is the realistic limit for air cooling, with the latter only likely if you’re using really good air. Bringing the VRM aboard may have improved overall performance in mobile, but it’s going to have repercussions for the overclocking crowd.
Whether you should upgrade depends a great deal on what you own right now. The i7-4770K is a better chip than the i7-3770K, and it includes features, like AVX2, that are going to be important to future processors. Given that most desktops currently enjoy a 5- to 6-year run, it’s reasonable to consider the future-proofing question. If your CPU model starts with “Core 2,” you could see CPU performance double by jumping to a new Haswell-equipped system from a 2006-2007 system.
Similarly, if you’re still using an original Core i7/Core i5, the benefits of a new chip are still going to be significant. A modern i7-4770K consumes significantly less power than a first-generation Core i7, clock speeds are higher, and Haswell could be 30% to 40% faster, clock for clock. Owners of Sandy Bridge- or Ivy Bridge-equipped PCs, however, are probably going to be fine with what they have already. Unless you have a major need for speed, Haswell isn’t a strong enough option to justify a brand-new system all on its own—at least, not on the desktop.
Mobile, supposedly, is going to be a different story. We say “supposedly” because we’ve not had a chance to evaluate any of the new laptops that Intel claims will deliver a 50% improvement in battery life. Based on our desktop measurements, Haswell’s power consumption has actually increased slightly, though this may only be a problem at the high end.
The Intel Core i7-4770K is a good chip that nevertheless underlines the difficulty of continuing to scale processor designs in the face of difficult manufacturing trends. If you held off on upgrading to Ivy Bridge because you wanted to see what Haswell would offer, there’s enough good stuff here to have made the wait worthwhile. If you bought a new desktop in the past three years, you may want to watch and see if the programs you run adopt AVX2 as a new instruction set before deciding to upgrade.
Copyright © 2012 Ziff Davis, Inc