If you're looking to build a moderately powerful PC at a reasonable price, you've got plenty of recently released CPU options here in late 2015—both Intel- and AMD-flavored. Which one is right for you depends largely on what you plan to do most often with your PC. On one side of the field resides AMD's self-described "accelerated processing units" (APUs, the company's combined CPUs/graphics processors), which are geared toward those who want very good integrated graphics performance at an affordable price. And having just looked at AMD's most recent top-end APU, the A10-7870K, we can say that it packs quite a graphical punch for its $135 asking price. (Its CPU performance lags behind that of similarly priced Intel chips.)
On the other side of the processor fence is Intel's mainstream 6th-Generation Core ("Skylake") line. At this writing, it was topped by the Core i7-6700K, a killer chip for those who prioritize CPU muscle. Most of Intel's chips these days also feature on-chip graphics, but they are generally outpaced by AMD's on-chip graphics.
Intel's Iris Pro-equipped Core i7-5775C ($250.00 at Amazon) does have better on-chip graphics than any current AMD APU, but it's also a much more expensive processor, currently selling for over $400. And the Core i7-5775C is part of Intel's now last-generation "Broadwell" 5th-Generation line, so you won't be seeing any new, more powerful options that will work in that chip's same LGA 1150 socket, should you want to upgrade down the line. It's the end of that particular road.
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The newer "Skylake" Core i7-6700K was around $360 at the time we wrote this, and occasionally a bit less on sale (if you can find it in stock, that is). It's still an expensive part if you're aiming to keep costs down. And while it's an impressive performer for multi-threaded workloads (think: video editing and most Adobe content-creation apps), much of its processing prowess isn't going to be felt in average, day-to-day computing tasks, including gaming.
For those looking to spend less on a processor for a new PC-building project, but who still want good performance for those times when you do want to edit video or throw some Photoshop filters at your fancy new camera's uncompressed RAW files, Intel's $260 Core i5-6600K is a good middle ground in terms of performance and price. Plus, it delivers the same easy overclocking options as its pricier Core i7 counterpart.
Just know that Hyper-Threading is disabled on this Core i5 chip, while its 91-watt thermal design power rating (TDP), the measure of how much heat a chip generates, remains the same as on costlier models in the Core line. The lack of Hyper-Threading could be a strike against this chip if you use heavily threaded programs that would otherwise have been able to make use of the four "virtual" processing threads that Hyper-Threading enables in other quad-core chips. But if your content-creation activities are casual and not how you make your living, you likely won't miss Hyper-Threading much.
Also note that, like the Core i7-6700K, this chip requires a new motherboard with an LGA 1151 socket. So you can't drop it into an existing Z97- or H97-chipset motherboard. We've been quite impressed with the new features that have landed on many of the new LGA 1151-equipped Z170 motherboards. Most of the new features have to do with extremely speedy storage via PCI Express x4 M.2 SSD slots and ports for USB 3.1 Gen 2, which doubles the theoretical bandwidth over USB 3.0. For details about these new features and others, be sure to check our review of the MSI Z170A Gaming M5, a sub-$200 board that delivers some of the best of what the new Z170 boards have to offer.
Skylake Basics: New Socket, New Chipsets
Intel's 5th-Generation Core chips arrived later than expected—especially for desktop enthusiasts and gamers. The first socketed "Broadwell" chip, the Iris Pro-packing Core i7-5775C, landed in our test bed (and on store shelves) nearly a year after the first low-power Core M 5th-Generation chips were announced in September of 2014.
Intel took a different tack with its 6th-Generation "Skylake" parts, treating enthusiasts and DIY builders to a couple high-end socketed desktop chips early in the "Skylake" unveiling, in the summer of 2015, a few months before its more-mainstream 6th-Generation laptop chips. These are just starting to show up in devices as we write this in mid-October 2015.
Specifically, Intel unveiled the four-core, four-thread Core i5-6600K that we're looking at here, and the quad-core, eight-thread Core i7-6700K. Rather than rattle off a full list of the chips' specs, here's a chart detailing the first two Skylake chips, direct from Intel...
Note that the Core i5 chip lacks Hyper-Threading, as we noted earlier. It also has a notably lower 3.5GHz base clock speed than the 3.9GHz of the Core i7 option. But the Core i5's top clock speed under the right thermal conditions (the "Turbo Frequency") sits at 3.9GHz—closer to the Core i7's 4.2GHz speed.
As noted up top, you'll need a new motherboard if you opt for the Core i5-6600K (or any 6th-Generation Core CPU), as the chips have an extra pin, and so use a socket called LGA 1151. While we'd love to see "Skylake" chips have backward-compatibility with older boards, those with LGA 1150-socket, Intel Z97-based boards, which came in late in the 4th-Generation Core game (with the "Devil's Canyon" Core i7-4790K), do have the option of installing a very recent 5th-Generation Broadwell CPU like the Core i7-5775C. That chip, in particular, has impressive Iris Pro graphics that, in our tests, blew past the new HD 530 GPU in the Core i5-6600K, while using a much lower power/heat envelope of 65 watts, compared to 91 watts on the Core i5 and i7 Skylake chips.
That "Broadwell" desktop chip, though, comprises the end of that particular line/socket. So there won't be any more-powerful upgrade options if you opt to stick with Z97 and the Core i7-5775C. If you decide to look future-ward and opt for a 6th-Generation chip, the top-end Z170 chipset that works in concert with the LGA 1151 socket brings some fairly substantive new features.
For starters, Z170 boards will support up to 20 PCI Express (PCIe) 3.0 lanes, rather than the eight lanes of PCIe 2.0 provided by standard Z97 boards. (That is in addition to the 16 PCIe 3.0 lanes provided by the CPU, which remains the same with "Skylake.") The extra lanes come thanks to an upgrade to the DMI interface that connects the CPU to the chipset, and they are important, given the rising prevalence of PCIe-based storage (via M.2, SATA Express, or drives that plug directly into a PCI Express slot, such as the card version of Intel's SSD 750 Series). This schematic summarizes it. (As you can see, this slide was produced in connection with the launch of the Core i7 version of the "Skylake" chip; it also applies to the Core i5.)
Considering we've yet to see a graphics card saturate even eight lanes of PCIe 3.0 (which has twice the bandwidth of PCIe 2.0), you should be able to install two graphics cards in a Z170-based system, as well as up to three PCIe x4 drives, and still have six lanes to spare for other peripherals like, say, a Thunderbolt-based RAID drive box or two.
Those who need more PCIe lanes, though, will still have to step up to the pricier Intel X99 platform, and its dearly priced chips like the Core i7-5960X Extreme Edition. But we suspect that all but the most extreme enthusiasts and digital-content producers will be satisfied with the PCIe bandwidth offered by the Z170 chipset.
The new chipset brings support for up to three PCIe-based drives in a system (and the option to RAID them together for even faster performance), while retaining support for six SATA 6Gbps ports. For external storage, Z170 now supports up to 10 native USB 3.0 ports (up from six in Z97 boards) and 14 USB 2.0 ports. There's no mention of USB 3.1, either type A or C, but we've seen support for that feature on quite a few midrange and high-end motherboards. Motherboard makers are just using separate chips, rather than native Intel-based support.
It's also worth noting that the new 6th-Generation chips technically support both DDR3 and DDR4 memory. That means, in some cases, you will be able to carry over older memory. But the vast majority of Z170 motherboards we have seen so far only have DDR4 slots, which are physically different than DDR3 slots. So unless you specifically seek out a DDR3-compatible board (and there won't be much of a selection), you'll need to spring for some new RAM as well.
Of course, other 100-family chipsets will also be on offer with lesser features, or with features designed for business users. We saw a host of these previewed in dribs and drabs at Computex 2015, and boards based on these other chipsets (the B150, Q170, and H110, among others) should launch in the coming months, along with further details about what features they will offer. But Z170 is the highest-end chipset in the lineup, so those looking for the best features, as well as support for high-end components, need not wait for those other boards and chipsets.
CPU Performance
We started our testing of the Core i5-6600K with a host of CPU-centric trials. Our Intel comparison chips were the aforementioned Core i7-6700K, the 4th-Generation, high-end Core i7-4790K "Devil's Canyon" and Core i7-4770K chips, and the more recent 5th-Gen Core i7-5775C (which has lower clock speeds but way more muscular Iris Pro graphics). As for AMD, we included AMD's two top chips in its FX line (the FX-8370 and FX-9590, and the new top-end APU, the AMD A10-7870K, which is more affordable than anything else here, currently selling for about $135.
For perspective (and kicks!), we also included the uber-powerful, eight-core Intel Core i7-5960X Extreme Edition, a $1,000 chip that, like the AMD FX processors, is a CPU only—no on-chip graphics acceleration. It runs on its own platform and socket.
Before we get into the benchmarking nitty-gritty, it's worth noting that while AMD's FX chips are power-hungrier, the FX-8370 still offers a fairly impressive amount of raw CPU performance for its current $200 asking price, so long as you don't need integrated graphics. Also note that we tested the Core i5-6600K, as well as the other chips here, under Windows 8.1, not Windows 10. While some users will have moved to Windows 10 by now (thanks in large part to the fact that it's a free upgrade for the first year), the new OS will likely deliver quite similar results to Windows 8.1 when it comes to CPU performance.
Plus, we'll need to do quite a bit of back-testing of processors and graphics cards before we officially switch to Windows 10 on the benchmark front—a task that we haven't had a chance to tackle just yet.
Cinebench R15
In Cinebench R15, an industry-standard benchmark test that taxes all available cores of a processor to measure raw CPU muscle, the Core i5-6600K didn't start out looking great, comparatively speaking.
It's no surprise that the new Core i5 chip was left behind by the Core i7-5960X (which costs roughly four times as much). And we'd expect the Core i7 chips here to surpass it as well, considering they can handle twice as many threads. But the $260 Intel Core i5 was slightly bested here by the $200 AMD FX-8370.
Keep in mind, though, that the AMD FX processor lacks any on-chip graphics, and it has a higher 125-watt TDP, compared to the Core i5-6600K's 91 watts.
iTunes 10.6 Conversion Test
We then switched over to our venerable iTunes Conversion Test, using version 10.6 of iTunes. This test taxes only a single CPU core, as much legacy software does.
Music encoding doesn't exactly push a modern CPU to its limits. But this test still illustrates that for older programs and those that haven't been written to take advantage of multiple cores, the Core i5 chip has a serious advantage over similarly clocked AMD offerings. The Core i5-6600K also managed to stick close here to the much-pricier Core i7-5775C.
Windows Media Encoder
Next up was our very, very well-aged Windows Media Encoder 9 video-conversion test. We continue to use this test and report its results because, like the iTunes test, it gives a window onto performance with legacy software that isn't fully threaded.
Here, we render a standard 3-minute-and-15-second video clip to a DVD-quality format...
Most recent high-end CPUs chew through this multi-threaded test in well under a minute. But because this is an older piece of software, it's not fully threaded to make use of all available cores. The Intel Core i5 continued its momentum here, easily besting all the AMD chips. And the Core i7 models weren't impressively speedier here, considering they have twice as many available computing threads and cost quite a bit more.
Handbrake 0.9.9
These days, our traditional Handbrake test (run under version 0.9.8) now takes less than a minute to complete with high-end chips. (It involved the rendering of a 5-minute video, Pixar's Dug's Special Mission, to an iPhone-friendly format.) So, we've switched to a much more taxing (and time-consuming) 4K video-crunching test.
In this test, we switched to the latest revision of Handbrake (version 0.9.9) and tasked the CPUs to convert a 12-minute-and-14-second 4K .MOV file (the 4K showcase short Tears of Steel) into a 1080p MPEG-4 video…
There's no denying that the Core i5-6600K was left behind here by the chips that have more cores and threads, like the Core i7-6700K and the i7-5960X Extreme Edition chip (which has eight cores and 16 threads). But the 6th-Generation Core i5 still managed to stick fairly close on this test to the much-pricier Core i7-5775C, while finishing a minute sooner than the fastest AMD chip in our charts.
Photoshop CS6
Next up, in our Photoshop CS6 benchmark, the Core i5-6600K looked even better, finishing dead-even with the $1,000 Extreme Edition processor (which sacrifices clock speed for more cores). In this test, we run a series of 11 filters, in sequence, on a labs-standard high-res photo, timing how long it takes the system to render the effect.
The Core i5-6600K looked good here against the recent Core i7 offerings, as well, lagging slightly behind, but staying fairly close to the 4th- and 5th-Generation options.
POV Ray 3.7
This was the last of our CPU-centric tests. Using the "All CPUs" setting, we ran the POV Ray benchmark, which challenges all available cores to render a complex photo-realistic image using ray tracing.
Here, the Core i5-6600K looked somewhat less impressive, besting the AMD FX-9590, but only landing even with the less-expensive AMD FX-8370. The Core i7-6700K finished 30 seconds sooner, while the Extreme Edition chip finished the same test in not much more than half the Core i5's time. This test, as well as Handbrake, proves the benefit of high-end chips with lots of available threads for tasks like video editing and other CPU-intensive media-creation tasks.
Overclocking
Early processors in Intel's "Haswell" 4th-Gen desktop line did not have great reputations as overclocking candidates. As a result, Intel made a fairly big deal about its improved thermal interface (between the die and the chip-top heat spreader) with 2014's Core i7-4790K "Devil's Canyon" CPU. Even so, we (and most reviewers) achieved middling-at-best results when attempting to overclock that chip.
This time around, we had better luck with the new 6th-Generation chips, achieving an impressive 4.85GHz top boost-clock speed with the Core i7-6700K using Asus' automatic AI Tweaker OC settings and a Thermaltake Water 2.0 Pro single-radiator cooler.
Using the same motherboard and cooler with the Core i5-6700K, we achieved a slightly lower top clock speed, 4.5GHz. But considering the Core i5 chip has a lower base clock speed than the Core i7 chip to start with, this ceiling wasn't surprising. We also didn't up the voltage, so those who dare to do so and spend more time tweaking may achieve better results.
Plus, of course, overclockability often varies between individual chip samples, so your mileage may (and probably will) vary somewhat. And if you don't pay close attention to your temperatures, you can damage your processor, so be sure you know what you're doing before aiming for high clock-speed and voltage settings.
With the top clock speed hovering around 4.5GHz in our best overclock, we saw our Cinebench R15 score jump from 602 at stock to 732 (a nearly 22 percent increase), while shaving nearly three minutes off the stock-clocked Core i5's transcoding time on our Handbrake 4K test (another improvement of roughly 20 percent). That doesn't quite push the overclocked Core i5 to stock Core i7 levels, but it gets the lesser chip significantly closer to its costlier cousin. But of course, the Core i7-6700K is easily overclocked as well, so it's all just a question of how much you care, and how much you are willing to spend.
Graphics Performance
You'll notice some changes to the comparison CPUs below in our graphics tests, versus the ones in our preceding CPU Performance section, to reflect current CPUs that have built-in graphics acceleration. (The Intel Core i7-5960X Extreme Edition and AMD FX chips from the previous charts lack it.)
Also, note that the Intel HD 530 graphics in the Core i5-6600K is identical (in both silicon and clock speed) to that found on the Core i7-6700K chip. So the results between those two "Skylake" chips are nearly identical, with the Core i5 occasionally falling slightly behind, likely due to its lower clock speed on the CPU side.
Note as well that the HD 530 graphics (a new naming scheme for Intel, which largely seems to involve dropping the last zero) on the Core i5-6600K and Core i7-6700K isn't meant to compete with the company's fastest Iris Pro graphics, found on the Core i7-5775C. But HD 530 does show improvements over the HD 4600 graphics found on the Core i7-4790K.
3DMark Fire Strike
We started out our graphics testing of the Core i5-6600K's HD 530 graphics with the 2013 version of Futuremark's 3DMark, specifically its high-end Fire Strike subtest, which is designed to measure a system's overall graphics capabilities.
By this measure, particularly the graphics subscore (which attempts to isolate the graphics capabilities from the rest of the system), the Core i5-6600K outpaced the "Haswell"-based Core i7-4790K by nearly 16 percent. The Core i7-6700K did about 2 percent better here, likely thanks to its higher-clocked CPU portion.
The Iris Pro graphics in the Broadwell-based Core i7-5775C performed much better, though (as we expected), eclipsing the HD 530 in the "Skylake" chip by a very large margin (67 percent). And AMD's A10-7870K held up here as a good value proposition for those who want affordable integrated graphics. The $135 AMD APU's graphics bested the $260 "Skylake" Core i5 chip's HD 530 by a healthy 69 percent.
Aliens Vs. Predator
Switching over to our aging-but-taxing DirectX 11 Aliens Vs. Predator game benchmark, we get our first sense of what kind of frame rates the Core i5 can deliver…
Here, the two "Skylake" chips performed essentially the same, both outperforming the "Haswell" Core i7s here. Again, though, Intel's Core i7-5775C was the only option that got even close to playable frame rates. Again, though, the AMD A10-7870K is the real winner if gaming performance (and value) is a priority, delivering very similar performance to the priciest Intel chip in this chart, while costing more than $200 less.
Tomb Raider & Sleeping Dogs
In more recent game titles such as Tomb Raider and Sleeping Dogs, we were able to attain playable frame rates with the Core i5-6600K at normal/medium graphics settings and a resolution of 1080p—though just barely. Still, with the Core i7-4790K or Core i7-4770K, you'd have to dip down to a lower resolution altogether to get smooth performance. Again, the AMD A10 held a strong lead over all the chips here save for the Core i7-5775C and its Iris Pro, which did substantively better on these benchmarks.
Tomb Raider's Ultra setting, though, proves that integrated graphics are still a poor choice for those who want to play modern demanding titles at anything more than middling settings. Even the Iris Pro and AMD's best A10 couldn't deliver smooth frame rates at 1080p with those settings.
Conclusion
We like the Z170 chipset's addition of more PCIe lanes for next-generation storage that takes matters (well) beyond the limitations of SATA. And new Intel Z170-based boards have brought other interesting features to the table, including multiple M.2 slots and support for USB 3.1 Gen 2 and USB-C connectors.
The new chipset and motherboard features help make Intel's chips generally more appealing than AMD's current chips, despite strong performance-for-the price offerings like the AMD A10-7870K and AMD FX-8350.
The Intel Core i5-6600K, specifically, is an interesting pick for price-conscious performance hounds. It's a solid performer that's a good fit for those looking to jump into the Z170 platform, who still want fast CPU performance for general-purpose computing and games, but who don't want to spend more than $300 for the Core i7-6700K.
But make no mistake: This is still a powerful CPU, and possibly well more powerful than you really need. If you rarely perform tasks that lean heavily on the CPU and all of its available cores, it's probably overkill. You could opt instead for a dual-core, four-thread Intel chip such as the Intel Core i3-6320, which has similarly high clock speeds and, according to Intel, should sell for about $100 less than the Core i5-6600K we're looking at here.
We say "should," because the Core i3 chip doesn't seem to be for sale yet. The Core i3 chip has been officially launched by Intel, though. So by the time you read this, the "Skylake" Core i3 may well be available at your favorite PC parts seller. If not, while it's a completely different platform, the AMD A10-7870K delivers very good integrated graphics performance and enough CPU horsepower for mainstream computing tasks, and it's readily available now for about $135. If your choice of CPU can coincide with a choice of platforms, you should weigh that AMD APU chip, too, if onboard graphics is your key buying point.
For a good mix of muscle, relative savings, and forward-looking architecture, though, the Core i5-6600K comes recommended. Just remember to factor the cost of a supporting mainboard and new DDR4 RAM into your buying formula.
Though limited to four cores/four threads, the Core i5-6600K is a strong pick for price-conscious performance hounds and future-looking gamers seeking a powerful CPU at a reasonable price.
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