Silicon and Process Nodes: 14++

Despite being somewhat reserved in our pre-briefing, and initially blanket labeling the process node for these chips as ‘14nm’, we can confirm that Intel’s newest ‘14++’ manufacturing process is being used for these 8th Generation processors. This becomes Intel’s third crack at a 14nm process, following on from Broadwell though Skylake (14), Kaby Lake (14+), and now Coffee Lake (14++).

With the 8th Generation of processors, Intel is moving away from having the generation correlate to both the process node and microarchitecture. As Intel’s plans to shrink its process nodes have become elongated, Intel has decided that it will use multiple process nodes and microarchitectures across a single generation of products to ensure that every update cycle has a process node and microarchitecture that Intel feels best suits that market. A lot of this is down to product maturity, yields, and progress on the manufacturing side.

Intel's Core Architecture Cadence (8/20)
Core Generation Microarchitecture Process Node Release Year
2nd Sandy Bridge 32nm 2011
3rd Ivy Bridge 22nm 2012
4th Haswell 22nm 2013
5th Broadwell 14nm 2014
6th Skylake 14nm 2015
7th Kaby Lake 14nm+ 2016
8th Kaby Lake Refresh
Coffee Lake
Cannon Lake
9th Ice Lake?
10nm+ 2018?
Unknown Cascade Lake (Server) ? ?

Kaby Lake was advertised as using a 14+ node with slightly relaxed manufacturing parameters and a new FinFET profile. This was to allow for higher frequencies and better overclocking, although nothing was fundamentally changed in the core manufacturing parameters. With Coffee Lake at least, the minimum gate pitch has increased from 70nm for 84nm, with all other features being equal.

Increased gate pitch moves transistors further apart, forcing a lower current density. This allows for higher leakage transistors, meaning higher peak power and higher frequency at the expense of die area and idle power.

Normally Intel aims to improve their process every generation, however this seems like a step ‘back’ in some of the metrics in order to gain performance. The truth of the matter is that back in 2015, we were expecting Intel to be selling 10nm processors en-masse by now. As delays have crept into that timeline, the 14++ note is holding over until 10nm is on track. Intel has already stated that 10+ is likely to be the first node on the desktop, which given the track record on 14+ and 14++ might be a relaxed version of 10 in order to hit performance/power/yield targets, with some minor updates. Conceptually, Intel seems to be drifting towards seperate low-power and high-performance process nodes, with the former coming first.

Of course, changing the fin pitch is expected to increase the die area. With thanks to HEKPC (via Videocardz), we can already see a six-core i7-8700K silicon die compared to a quad-core i7-7700K.

The die area of the Coffee Lake 6+2 design (six cores and GT2 graphics) sits at ~151 mm2, compared to the ~125 mm2 for Kaby Lake 4+2 processor: a 26mm2 increase. This increase is mainly due to the two cores, however there is a minor adjustment in the integrated grpahics as well to support HDCP 2.2, not to mention any unpublished changes Intel has made to their designs between Kaby Lake and Coffee Lake.

The following calculations are built on assumptions and contain a margin of error

With the silicon floor plan, we can calculate that the CPU cores (plus cache) account for 47.3% of the die, or 71.35 mm2. Divided by six gives a value of 11.9 mm2 per core, which means that it takes 23.8 mm2 of die area for two cores. Out of the 26mm2 increase then, 91.5% of it is for the CPU area, and the rest is likely accounting for the change in the gate pitch across the whole processor. 

The Coffee Lake 4+2 die would then be expected to be around ~127 mm2, making a 2mm2 increase over the equivalent Kaby Lake 4+2, although this is well within the margin of error for measuring these processors. We are expecting to see some overclockers delid the quad-core processors soon after launch.

In previous Intel silicon designs, when Intel was ramping up its integrated graphics, we were surpassing 50% of the die area being dedicated to graphics. In this 6+2 design, the GPU area accounts for only 30.2% of the floor plan as provided, which is 45.6 mm2 of the full die.

Memory Support on Coffee Lake

With a new processor generation comes an update to memory support. There is always a small amount of confusion here about what Intel calls ‘official memory support’ and what the processors can actually run. Intel’s official memory support is typically a guarantee, saying that in all circumstances, with all processors, this memory speed should work. However motherboard manufacturers might offer speeds over 50% higher in their specification sheets, which Intel technically counts as an overclock.

This is usually seen as Intel processors having a lot of headroom to be conservative, avoid RMAs, and maintain stability. In most cases this is usually a good thing: there are only a few niche scenarios where super high-speed memory can equate to tangible performance gains* but they do exist.

*Based on previous experience, but pending a memory scaling review

For our testing at least, our philosophy is that we test at the CPU manufacturers’ recommended setting. If there is a performance gain to be had from slightly faster memory, then it pays dividends to set that as the limit for official memory support. This way, there is no argument on what the rated performance of the processor is.

For the new generation, Intel is supporting DDR4-2666 for the six-core parts and DDR4-2400 for the quad-core parts, in both 1DPC (one DIMM per channel) and 2DPC modes. This should make it relatively simple, compared to AMD’s memory support differing on DPC and type of memory.

It gets simple until we talk about AIO designs using the processors, which typically require SODIMM memory. For these parts, for both quad-core and hex-core, Intel is supporting DDR4-2400 at 1DPC and DDR4-2133 at 2DPC. LPDDR3 support is dropped entirely. The reason for supporting a reduced memory frequency in an AIO environment with SODIMMs is because these motherboards typically run their traces as chained between the memory slots, rather than a T-Topology which helps with timing synchronization. Intel has made the T-Topology part of the specification for desktop motherboards, but not for AIO or integrated ones, which explains the difference in DRAM speed support.

These supported frequencies follow JEDEC official sub-timings. Familiar system builders will be used to DDR4-2133 at a CAS Latency of 15, but as we increase the speed of the modules, the latency increases to compensate:

Intel’s official sub-timing support at DDR4-2666 is 19-19-19. Outside of enterprise modules, that memory does not really exist, because memory manufacturers can seem to mint DDR4-2666 16-17-17 modules fairly easily, and these processors are typically fine with those sub-timings. CPU manufacturers typically only state ‘supported frequency at JEDEC sub-timings’ and do not go into sub-timing discussions, because most users care more about the memory frequency. If time permits, it would be interesting to see just how much of a performance deficit the official JEDEC sub-timings provide compared to what memory is actually on sale.

The Intel Coffee Lake Early Review Physical Design, Integrated Graphics, and the Z370 Chipset: Differences
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  • mapesdhs - Monday, October 9, 2017 - link

    I'm not sure. :D It's certainly annoying though. Worst part is searching for anything and then changing the list order to cheapest first, what a mess...
  • SunnyNW - Thursday, October 5, 2017 - link

    "That changes today."

    Anyone else read that and think that it is something we should have been reading ages ago?
    Consumer technology is progressing slower than many expected and I feel the same way. Nonetheless I can't help but envision a Very near future where I'll be coming back and reading this article and being depressed at this level of technology all the while on my future monolithic many thousand core 3D processor ;)
  • KAlmquist - Friday, October 6, 2017 - link

    Yes. A year ago this would have been an exciting development. Now it's just Intel remaining competitive against AMD's offerings.
  • Valcoma - Thursday, October 5, 2017 - link

    "The Core i5-8400 ($182) and Core i3-8350K ($169) sit near the Ryzen 5 1500X ($189) and the Ryzen 5 1400 ($169) respectively. Both the AMD parts are six cores and twelve threads, up against the 6C/6T Core i5 and the 4C/4T Core i3. The difference between the Ryzen 4 1400 and the Core i3-8350K would be interesting, given the extreme thread deficit between the two."

    Those AMD parts are 4 cores, 8 threads.
  • Ian Cutress - Thursday, October 5, 2017 - link

    You're right, had a brain spasm while writing that bit. Updated.
  • kpb321 - Thursday, October 5, 2017 - link

    Still off

    "The difference between the Ryzen 5 1500X and the Core i3-8350K would be interesting, given the extreme thread deficit (12 threads vs 4) between the two."

    the 1500X is a 4c8t processor so it effectively has hyper-threading over the i3-8350K while having a lower overclocking ceiling and lower ipc.
  • Zingam - Saturday, October 7, 2017 - link

    Drinking too much Coffee, eh?
  • hansmuff - Thursday, October 5, 2017 - link

    Ian, I love the way the gaming benchmarks are listed. So easy to access and much less confusing than drop-downs or arrows. Nice job!
  • Valcoma - Thursday, October 5, 2017 - link

    Are you sure that the i5-7400 got 131 FPS average in benchmark 1 - Spine of the Mountain in Rise of the Tomb Raider? Besting all the other vastly superior processors?

    Looks like a typing error there or something went wrong with your benchmark (lower settings for example on that run).
  • Ian Cutress - Thursday, October 5, 2017 - link

    I've mentioned it in several reviews in the past: RoTR stage 1 is heavily optimized for quad core. Check our Bench results - the top eight CPUs are all 4C/4T. The minute you add threads, the results plummet.

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