Intel’s 6th Gen Skylake Conclusions

The new 6th Generation Skylake platform from Intel has launched today, and as part of the package there are two new processors, the Core i7-6700K and the Core i5-6600K, a new Z170 motherboard chipset with corresponding motherboards, and also a new market for DDR4 DRAM. The purpose of the Skylake platform launch is to update the mainstream PC market segment for the purposes of better performance and enhanced connectivity.

What is Skylake?

Skylake is a new processor architecture based on Intel’s 14nm process using the newest generation of their FinFET lithographic technology, and the two overclockable K series CPUs are the first processors to be released into the wild. For some this is mildly confusing, given that Intel launched Broadwell for desktop (a die shrink "tick" from 22nm to 14nm) only a couple of months ago. Broadwell has only acted as a minor stopgap measure, fulfilling the requirements of an upgradable platform and taking the crown of the best integrated graphics processor for a socket. As a result of that minor role, a number of users will see Skylake more as an upgrade from Haswell, the last mainstream processor family that had a long market shelf life.

For this launch and review, details about Skylake have been relatively rare to come by even in Intel’s own press documents, and we are set to hear more details at Intel’s Developer Forum in mid-August. Nonetheless, we have been able to determine that Skylake has a raft of updates, focusing on fixed function hardware to accelerate certain workloads as well as decoupling the CPU and PCIe frequency domains on the silicon to allow for more precise overclocking.

The platform changes as well. The voltage regulators inside Haswell CPUs move back out on to the motherboard as they generated too much heat inside the CPU. This is good for overclockers, but means the required components on Z170 motherboards, and price, has the potential to go up. The Z170 chipset is the sole chipset being released today, with others coming later in the year. Z170 features an upgrade to DMI 3.0, giving faster CPU-to-chipset bandwidth and enabling a 26-lane high speed IO hub. Of these lanes, 20 can be configured for PCIe lanes under a strict set of rules, giving access to the potential for more functionality on board. Most motherboards being launched today will use these lanes to provide M.2 slots, USB 3.1 Gen 2 ports via controllers, extra networking, extra PCIe slots and SATA Express connectivity. In our motherboard overview we have details on over 55 motherboards to look through.

The Results

Overall, Skylake is not an earth shattering leap in performance. In our IPC testing, with CPUs at 3 GHz, we saw a 5.7% increase in performance over a Haswell processor at the same clockspeed and ~ 25% gains over Sandy Bridge. That 5.7% value masks the fact that between Haswell and Skylake, we have Broadwell, marking a 5.7% increase for a two generation gap.

In our discrete gaming benchmarks, at 3GHz Skylake actually performs worse than Haswell at an equivalent clockspeed, giving up an average of 1.3% performance. We don’t have much from Intel as to analyze the architecture to see why this happens, and it is pretty arguable that it is noticeable, but it is there. Hopefully this is just a teething issue with the new platform.

When we ratchet the CPUs back up to their regular, stock clockspeeds, we see a gap worth discussing. Overall at stock, the i7-6700K is an average 37% faster than Sandy Bridge in CPU benchmarks, 19% faster than the i7-4770K, and 5% faster than the Devil’s Canyon based i7-4790K. Certain benchmarks like HandBrake, Hybrid x265, and Google Octane get substantially bigger gains, suggesting that Skylake’s strengths may lie in fixed function hardware under the hood.

In full speed gaming benchmarks we have some situations that benefit from Skylake (GRID on high end graphics cards) and others that drop (Mordor on GTX 770), but the important aspect to consider is despite Skylake supporting both DDR3L and DDR4 memory, our results show that even with a fast DDR3 kit, a default-speed DDR4 set of memory is still worth upgrading to. On average there’s a small change in performance in favor of the DDR4 (especially in integrated graphics), but DDR4 confers benefits such as more memory per module and lower voltages to aid power consumption

A quick turn to the overclocking situation on Skylake: from our small sample set, most of the CPUs achieved 4.6 GHz when pushing and 4.5 GHz comfortably, including the retail sample that had 4.5 GHz. Speaking to other reviewers, their results match us or even slightly better our own, with one report of a 5.0 GHz gem of a processor. From our testing, Skylake seems to have more of a temperature barrier than a voltage barrier, so increasing the cooling seems to be the task of the day here to get the high frequencies.

With all that, I’m going to make a bold statement.

Sandy Bridge, Your Time Is Up.

A large number of users invested into Intel based platforms during the Core 2 Quad, Nehalem and Sandy Bridge releases. Sandy Bridge was notable because it inferred a large performance gain at stock speeds, and with a good processor anyone could reach 4.7 GHz and even higher using a good high end cooler. With that, Intel has had a problem enticing these users to upgrade because their performance has been constantly matched by Ivy Bridge, Haswell and Broadwell – for every 5% IPC increase from the CPU, an average 200 MHz was lost on the good overclock and they would have to find a good overclocking CPU again. There was no great reason, apart from chipset functionality to upgrade.

That changes with Skylake.

From a clock-to-clock performance perspective, Skylake gives an average ~25% better performance in CPU based benchmarks, and when running both generations of processors at their stock speeds that increase jumps up to 37%. In specific tests, it is even higher.  When you scale up to a 4.5 GHz Skylake against a 4.7 GHz Sandy Bridge, the 4% frequency difference is only a tiny portion of that. There are other added benefits, such as the move to a DDR4 memory topology that has denser memory modules, as well as PCIe storage and even PCIe 3.0 graphics connectivity.

As I said above, Skylake is not necessarily the most ground breaking architecture over Haswell. It affords a 19% CPU performance gain over the i7-4770K and 5% over the i7-4790K. There is a small minor issue with gaming that disappears when you use synthetics, but only to the tune of a couple of percentage points. For that minor hit, the package combo of processor, chipset and DDR4 should be an intrigue in the minds of Sandy Bridge (and older) owners.

What Happens Now?

Next on the list for us is Intel’s Developer Forum in mid-August. Here Intel has said they will present details on their Skylake architecture and it will hopefully shed some further insight into what is going on under the hood with Skylake. We will have a full write up for you after the event.

There is still the rest of the Skylake stack to be released – non overclocking processors, low power processors, and the B/H/Q chipsets too. There is no official date on these except ‘later in the year’. We will also get to these when we have more information.

What You Can Buy: Gaming Benchmarks on High End GPUs
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  • stux - Friday, August 7, 2015 - link

    I upgraded my 920 to a 990x, it runs at about 4.4ghz on air in an XPC chassis! and has 6/12 cores.

    I bought it off ebay cheap, and with an SSD on a SATA3 card I see no reason to upgrade. It works fantastically well, and is pretty much as fast as any modern 4 core machine.
    Reply
  • Samus - Sunday, October 25, 2015 - link

    If you single GPU and don't go ultra-high-end then gaming is still relevant on x58, but it really isn't capable of SLI due to PCIe 2.0 and the lanes being reduced to 8x electrical when more than one 16x length slot is used. QPI also isn't very efficient by todays standards and at the time, AMD still had a better on-die memory controller, but Intel's first attempt was commendable, but completely overhauled with Sandy Bridge which offered virtually the same performance from 2 channels. Anybody who has run dual channel on X58 knows how bad it actually is and why triple channel is needed to keep it competitive with todays platforms.

    I loved X58. It is undoubtedly the most stable platform I'd had since the 440BX. But as I said, by todays standards, it makes Sandy Bridge seem groundbreaking, not because of the IPC, but because of the chipset platform. The reduced power consumption, simplicity and overall smaller-size and lower cost of 60/70 series chipsets, then the incredibly simplified VRM layout in 80/90 chipsets (due to the ondie FIVR of Haswell) makes X58 "look" ancient, but as I said, still relevant.

    Just don't load up the PCIe bus. A GPU, sound card and USB 3.0 controller is about as far as you want to go, and for the most part, as far as you need too!
    Reply
  • vdek - Thursday, August 6, 2015 - link

    Get a Xeon 5650, 6 core CPU, 32nm, will run at 4-4.2ghz all day on air. I upgraded my i7 920 the X5650 and I couldn't be happier. They go for about $70-80 on amazon or ebay. I'm planning on keeping my desktop for another 2-3 years, I upgraded the GPU to a GTX970 and it maxes out most of what I can throw at it. I don't really see my CPU as a bottleneck here. Reply
  • mdw9604 - Tuesday, August 11, 2015 - link

    Can you OC a Xeon 5650? Reply
  • mapesdhs - Wednesday, August 12, 2015 - link

    Of course, back then the main oc'ing method was still bclk-based based, though X58 was a little more involved than that compared to P55 (uncore, etc.) Reply
  • LCTR - Saturday, August 15, 2015 - link

    I'd been pondering the 6700K until I saw these posts from 920 users :)
    I use mine for gaming / video editing, it's running non-hyperthreaded at 4.2GHz on air (about 4Ghz with HT on)

    I also upgraded my GPU to a 970 and have seen decent gaming performance - if I could jump to a X5650 and stretch things for 1-2 years that'd be great...

    What sort of performance do you see from the X5650? Would it win 4GHz with HT enabled?
    The Xeon 5650's don't need any special mobo support or anything, do they? I have a gigabyte GA-EX58-UD5

    Reply
  • Nfarce - Wednesday, August 5, 2015 - link

    Well sadly, ever since SB (which I have one that's 4 years old, a 2500K, alongside a newer Haswell 4690K, each new tick/tock has not been much. The days of getting 50% boost in performance between a few generations are long gone, let alone 100% boost, or doubling performance. Also keep in mind that there is a reason for this decrease in increased performance: as dies shrink, physics with electrons start becoming an issue. Intel has been focusing more on decreased power usage. At some point CPU manufacturers will need to look at an entirely different manufacturing material and design as silicon and traditional PCB design is coming to its limit. Reply
  • Mr Perfect - Wednesday, August 5, 2015 - link

    It's not even 30% in high-end gaming. There is a clear improvement between SB and Skylake, but why should I build a whole new PC for 5FPS? I can't justify that expense.

    I'd be curious to see the high-end gaming benchmarks rerun with the next generation of GPUs. Will next gen GPUs care more about the CPU, or does DX12 eliminate the difference altogether?
    Reply
  • mkozakewich - Thursday, August 6, 2015 - link

    It's unlikely you'll be seeing doubles and doubles anymore. If you look at what's been going on for the past several years, we're moving to more efficient processes instead of improving performance. I'm sure Intel's end goal is to make powerful CPUs for devices that fit into people's pockets. At that point you might see more start going into raw performance. Reply
  • edlee - Wednesday, August 5, 2015 - link

    i am not sure why conclusion to the review makes it seem i7-2600k users should upgrade to this.
    If you are a gamer, there is no 25% improvement in average or minimum frame rate, its 3-6% at best.

    Is this the future of intel's tock strategy, to give very little improvement to gamers?
    Reply

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