The AnandTech Coffee Lake Review: Initial Numbers on the Core i7-8700K and Core i5-8400by Ian Cutress on October 5, 2017 9:00 AM EST
- Posted in
- Core i5
- Core i7
- Core i3
- Coffee Lake
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|
|8th||Kaby Lake Refresh
|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.
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FireSnake - Thursday, October 5, 2017 - linkAwesome revies! Let's read...
prisonerX - Thursday, October 5, 2017 - linkNo need, here is a quick summary: "Intel blind panic."
StevoLincolnite - Thursday, October 5, 2017 - linkAt-least they have finally soundly beat my 3930K in the mainstream after 6 years.
Still. No point me upgrading just yet.
mapesdhs - Friday, October 6, 2017 - linkEven then there's an interesting option if you want threaded performance; I just upgraded to a XEON E5-2680 v2 (IB-EP) for 165 UKP. Lower 1T speed for sure, but MT should be the same or better as a 3930K @ 4.8. No oc means more stable, less heat/noise/power, and being IB-based means it ups the slots to PCIe 3.0. Not a relevant choice for gaming, but a possibility for those doing VMs, rendering, etc., and just want to get by for a little while longer.
Breit - Friday, October 6, 2017 - linkOR search for an XEON E5-1680v2... :)
It's an Ivy Bridge-E 8c/16t chip that will fit in Sandy Bridge-E mainboards (x79) and has an unlocked multiplier opposed to this E5-2680v2. So with this you won't lose your overclocking ability.
But in the end, I guess that the greatly reduced power draw and the more "modern" platform from an i7-8700K system compared to the x79 platform will give it the edge here.
mapesdhs - Monday, October 9, 2017 - linkVery interesting that the 1680 v2 is unlocked, I didn't know that.
Alas though, availability of the 1680 v2 is basically zero, whereas the 2680 v2 is very easy to find, and the cost of 1680 v2s which are available (outside the UK) is extremely high (typical BIN of 600 UKP, normal auction start price of 350 UKP, completed listings only shown for BIN items which were purchased for between 500 and 600 UKP). By contrast, I bought several 2680 v2s for 165 UKP each. Testing on a P9X79 WS (all-core turbo of 3.1) gives a very impressive 15.44 for CB 11.5, and 1381 for CB R15 which is faster than a stock 8700K (for reference, the 1680 v2 scores 1230 for CB R15). Note the following page on AT has a very handy summary of all the turbo bin levels:
So, I'm very pleased with the 2680 v2 purchase, it's faster than my 3930K @ 4.8, runs with very low temps, much lower power draw, hence less heat, less fan noise and since it's not oc'd it'll be solidly reliable (this particular test system will eventually be in an office in India, so power/heat/reliability is critical). For the target systems in question, it's a great solution. Only thing I noticed so far is it didn't like me trying to set a 2133 RAM speed, but it worked ok at 1866; I can probably tighten the timings instead, currently just at 9/11/10/28/2T (GSkill 32GB kit, 8x4GB).
The 4930K I have though will go into my gaming system (R4E), since I don't mind the oc'ing fun, higher noise, etc., but it's not a system I'll use for converting video, for that I have a 6850K.
MrSpadge - Friday, October 6, 2017 - linkFull throttle: yes. Panic: no. Blind: no.
Zingam - Saturday, October 7, 2017 - linkCan you buy it? No? Paper launch of Unobtanium 8000? -> panic, PR propaganda bullshit and dirty Intel marketing tactics as usual targeted at lamer fanboys.
This comment is written by an Intel user! ;)
prisonerX - Saturday, October 7, 2017 - linkWe've got enough dumb Intel apologists here already, thanks.
coolhardware - Sunday, October 8, 2017 - linkThe i7-8700 is *finally* going to replace my trusty i5-2500K.
Ordered my 8700 on Amazon http://amzn.to/2y9IamG ($319) and looking forward to a nice upgrade :-) That is a lot of CPU for the money IMHO.
Kudos to AMD for bringing competition back to the CPU market!