Intel To Challenge AMD With 48 Core “Cascade Lake” Xeon AP

AMD is hosting its “Next Horizon” datacenter event in San Francisco this week, and archrival Intel, which is losing some market share to AMD but not feeling the pain on its books yet thanks to a massive buildout in server infrastructure at hyperscalers, cloud builders, and smaller service providers like telcos, is hitting back by divulging some of its plans for next year’s “Cascade Lake” Xeon lineup.

If all goes well, AMD is going to be first to market with a 7 nanometer chip when the Rome Epycs debut next year, and with Intel having bigtime issues that won’t see it deliver its “Ice Lake” Xeons until early 2020 in volume, Intel has to do something. And that something is to mimic what AMD is doing, and as it has done itself when under pressure from AMD in the server space in years gone by, and that is to cram two whole processors into a single socket to jack up the core count and memory controllers with the Cascade Lake Advanced Processors, or CLX-AP for short in the Intel lingo.

Lisa Spelman, general manager of Xeon and datacenter marketing at Intel, prebriefed the press on some of the details about the Cascade Lake AP processors ahead of the AMD event, and it is clear that Intel wants to be a spoiler and make everyone think twice about the Epycs. We covered the future roadmap for Xeons – including the Cascade Lake, Cooper Lake, and Ice Lake chips due in the next two years – in detail here and went into the standard, single chip module (SCM) variants of the Cascade Lake there. So we are not going to repeat all of that again, except that Intel is going to try to counter AMD’s Rome chips based on 7 nanometer chip making processes with the Cascade Lakes etched from refined 14 nanometer processes.

This is not the first time that Intel had to cram two Xeons into a socket to take on AMD. Way back in October 2005, in the wake of AMD getting the first dual-core Opteron X86 server processors to market (based on a monolithic design), Intel cooked up the “Paxville” Xeon DP chips, its first multicore module (MCM) implementation in the Xeon line and clearly a stop-gap measure at the time. Having MCMs is not a stop-gap anymore, but really the only practical answer to trying to put more cores into a socket without having the price of the chip and its thermals go through the roof. The thermals for the Cascade Lake AP Xeon might go through the roof just the same, if history is any guide.

To make a “Naples” Epyc 7000 series processor, AMD takes an eight-core Ryzen chiplet with two memory controllers and uses some PCI-Express 3.0 interconnect lanes to create an “Infinity Fabric’ that lashes them together to present themselves as a very tightly coupled baby NUMA server in a socket with 32 cores and eight memory controllers. Other PCI-Express lanes are available to be used as I/O or to create a two-socket chip.

Intel is not precisely doing this. Rather, it is taking a future Cascade Lake part with three UltraPath Interconnect (UPI) links that are used to link multiple servers into various NUMA topologies and cross-coupling the two chips together so it creates what looks, to the outside world, like a 48-core socket with twelve memory controllers on it. Like this:

Intel has taken a beating in some regards because its top-end “Skylake” Xeon SP-8180M Platinum chip, which packs 28 cores on a die, burns at 205 watts and only has six memory controllers. So the AMD Epycs as well as the Cavium ThunderX2 and IBM Power9, have a 33 percent advantage when it comes to memory capacity and memory bandwidth. These monolithic Skylake Xeon chips are also expensive compared to prior generations of Xeon chips, and probably have relative bad yield even if they are made on refined 14 nanometer processes that are getting pretty mature because they are such large chips. Intel can’t really cram more cores on a tie when it is stuck at 14 nanometers, hence the MCM.

In this case, the MCM will have two 24-core dies, each with the six memory controllers like the Skylake dies have. There is not one Skylake Xeon SP processor, but rather three different ones, and we think the die layout will remain essentially the same for Cascade Lake SP chips, which we know top out at 28 cores. (Intel has added some performance enhancements, hardware mitigations against the Spectre/Meltdown speculative execution vulnerabilities, and the VNNI deep learning acceleration instructions with Cascade Lake SPs.) The LCC variant of the Skylake and Cascade Lake Xeons has up to 10 cores on a mesh interconnect, the HCC variant has up to 18 cores, and the XCC variant has up to 28 cores. So it looks like Intel is taking something akin to the 24-core Xeon SP-8160M, which runs at 2.1 GHz and which costs half what the top-bin Xeon SP-8180M with 28 cores running at 2.5 GHz costs, and gussying it up with those extra Cascade Lake features and then popping two of them in a single socket.

“It is our intent and design to deliver performance leadership throughout 2019,” says Spelman. Ah, but you can never forget about price or about thermals, which Spelman did not mention. This is probably not an oversight on Spelman’s part, since the MCM version is probably going to have to gear back clocks to cram two 24-core chips into a single socket. And even then, this could end up being a 250 watt or maybe even a 275 watt or 300 watt part. So Intel could meet or beat AMD on performance, slash prices like crazy (with this 48-core Cascade Lake AP part not costing much more than a monolithic top-bin 28-core Skylake part), and still lose out bigtime on performance/watt and cost/performance/watt.

Everyone has the physics and thermodynamics concepts here. “For those who are power constrained, we have options,” says Spelman. “And for those who are performance constrained, we have options.” Just like during the Paxville Xeon days, which were a stopgap until Intel could get true dual-core monolithic dies out the door a year later.

This is sounding very familiar, only this time the rush is to perfect MCMs. They are now a given, thanks to the slowing down of Moore’s Law.

We have little doubt that using that third UPI link coming off each Cascade Lake XCC die to cross couple the two chips on the Cascade Lake AP package will have a performance advantage compared to the current Naples Epyc 7000s, since the UPI links have more bandwidth and lower latency than PCI-Express 3.0 lanes and because there are only two chips in the socket (one hop either way) compared to the Naples chiplets, which are either one or two hops away from each other, depending.

This two-chip Cascade Lake AP module will, says Spelman, offer up to 3.4X the Linpack double precision matrix math performance of a 32-core Epyc 7601 from Intel, and will deliver 30 percent more memory bandwidth performance based on the STREAM Triad memory bandwidth test. Considering that there are 50 percent more memory controllers on the Intel chip than on the AMD chip in this comparison, it looks like Intel has to slow the DDR4 memory controllers and the DDR4 memory sticks down a bit to save power. Separate from the chart above, Intel tells The Next Platform that the 48-core Cascade Lake chip will have 21 percent more oomph on Linpack than the top-bin Skylake Xeon SP-8180M Platinum chip with 28 cores running at 2.5 GHz, and if you do some rough math, that puts the clock speed of the Cascade Lake AP at around 1.8 GHz. On the STREAM Triad test, the future Cascade Lake AP MCM will beat the top-bin Skylake Xeon SP SCM by 83 percent, which is pretty good, but will only be 30 percent better than the AMD Epyc 7601.

The Cascade Lake SP and AP chips will come out all at the same time, which is during the first half of 2019 – about the same time AMD will roll with the Rome Epycs – if Taiwan Semiconductor Manufacturing Corp doesn’t hit any snags with its 7 nanometer processes.

We will see what AMD has to say this week out in San Francisco, and then take stab at trying to figure out how it will map to what Intel is doing. We have heard on the rumor mill that Rome Epycs will have 48 cores (as we expected) and only eight memory channels (we were hoping for more, but Rome has to be socket compatible with Naples); others are expecting AMD to crank Rome up to 64 cores in a socket, and still others say Rome is 48 cores and the kicker “Milan” processors will reach up to 64 cores. Intel just forced AMD’s hand into disclosure.

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4 Comments

  1. For the record. The Skylake Xeon SP-8180M, with an advertised clock of 2.5ghz does not run at that speed when running linpack on all cores. It throttles clock speed considerably when maxing out all the vector units. So it may not be safe to assume that the cascadelake AP will be 1.8ghz. I’m sure that with only a few cores busy it’ll clock up pretty high, but fall off when they all get busy.

  2. “Each Zeppelin die can create two PCIe 3.0 x16 links, which means a full EPYC processor is capable of eight x16 links totaling the 128 PCIe lanes presented earlier. AMD has designed these links such that they can support both PCIe at 8 GT/s and Infinity Fabric at 10.6 GT/s,” – https://www.anandtech.com/show/11551/amds-future-in-servers-new-7000-series-cpus-launched-and-epyc-analysis/2

    “Intel UPI uses a directory-based home snoop coherency protocol, which provides an operational speed of up to 10.4 GT/s” – https://software.intel.com/en-us/articles/intel-xeon-processor-scalable-family-technical-overview

    Infinity Fabric links are just barely faster than UPI (10.6 GT/s vs 10.4 GT/s) when connected die to die or socket to socket. Though latency seems likely to favor Cascade Lake. It’s not accurate to say UPI links have more bandwidth than Infinity Fabric.

  3. “To make a “Naples” Epyc 7000 series processor, AMD takes an eight-core Ryzen chiplet with two memory controllers and uses some PCI-Express 3.0 interconnect lanes to create an “Infinity Fabric’ that lashes them together to present themselves as a very tightly coupled baby NUMA server in a socket with 32 cores and eight memory controllers. Other PCI-Express lanes are available to be used as I/O or to create a two-socket chip.”

    No That’s a Zen/Zeppelin DIE that’s used for Epyc/Naples(4 Zen/Zeppelin SOC DIEs on an MCM) and Ryzen is a brand name for a consumer line of processors made from various Binned Zen/Zeppelin Server SOC DIEs(1 die for Ryzen-1 and 2 dies for Threadripper-1), with some of the server parts disabled. And I really suspect that the NextPlatform is an American publication now because any British Publication would take the time to get the AMD nomenclature correct. So that “Chiplet” is not called Ryzen and it’s Fabbed on a 14nm GF(Licensed from Samsung) process node and has been coming off GF’s diffusion lines at a better than 80% usable Die/Wafer yield rate.

    AMD’s first generation Zen/Zeppelin DIE was first and formost designed for server usage with the top 5% going towards Epyc 7000 series production with any Zen/Zeppelin dies that could not make the grade being binned for consumer usage(Ryzen-1 and Threadripper-1 SKUs).

    It should be noted that the 2nd generation Ryzen-2(Consumer) and Threadripper-2(Consumer HEDT) SKUs are obtained from a New Zen+(Minimal Tweaking of the Zen CPU Core/Uncore) Die(8 total Cores/2 CCX Units) on GF’s 12nm process while first generation Zen/Zeppelin(8 total cores/2 CCX units) Die is still produced using that 14nm(Licensed from Samsung Process) for any current/continuing first generation Zen Epyc/Naples production. And it sure took long enough to get the first generation 14nm Zen Epyc/Naples SKUs Vetted/Certified for production server workloads.

    Zen2 on TSMC’s 7nm node, well that’s really the new CPU microarchitectural update that going to produce a much larger IPC gain. There are rumors of an at least 15% gain in Zen2 IPC over Zen1 and most likely for the server market a little higher clocks at a much greater power/thermal efficiency. That “Zen+” spin(New Stepping on a new Less than Half Node shrink really) is just for the consumer market on an interim basis for a little higher clock speed/fixed latency issue and higher DIMM/DRAM memory clocks(beyond JEDEC standards) supported for the consumer/gaming market. GF’s 12nm node did have some Transistor Tweaking for better leakage and gate resistance metrics but nowhere near what TSMC’s 7nm is expected to provide on that full node shrink.

    Now for Zen2 and Epyc/Rome there is also talk of greatly increased L3 cache sizes and probably some new L1$ and L2$ allotments also, but there is also speculation on maybe 8 smaller Zen2/Zeppelin Dies(NON SOC), still at 8 cores each, surrounding a large central SOC die that provides the Memory Controllers and other off module services(SOC services die part on the MCM on Zen2/Epyc-2 SKUs). But that’s just some wild speculation on a possible new Epyc/Rome Die/Fabric topology that hopefully will be put to rest(Pro or Con) on Oct 6 at AMD’s yearly Investor Update event. PCIe 4.0 support would be a big plus for Epyc/Rome and I’d assume that would be compatable with current Epyc/SP3 MB’s PCIe PHY but I’m no expert on MBs or PCIe. So whatever the rumors concerning Zen2 Epyc/Rome(2nd generation Epyc) there is plausable speculation of 48 or 64 cores per Epyc/Rome MCM and more cores and threads all around that has made Intel feel the need to match on some level of at least 48 cores, on paper, until the hardware actually arrives as a product that’s certified/vetted for production server workloads, a long and involved process for any CPU maker.

    Also there are a line of “P” branded Epyc 7000 series parts that are for single socket usage that do not do a take-over on any PCIe lane PHY, but at least the total numbers of available PCIe 3.0 lanes remains 128 across any EPYC/SP3 MB platform, be it 1P or 2P, as AMD does not currently segement on PCIe lane counts like Intel does.

    So Intel is now grown fond of that Glue but still only two of those larger dies that will still come in at rather poor die/wafer yields and Intel’s binning operation has got to be one of the most complex in the industry what with all the product segementation that Intel engages in.

    Now Intel is out with news on this new SKU(release date some time in 2019) and some more of that marketing spin that’s really needing the fine print made larger for folks with 20 20 to be able to read. And of course the Dell Boy benchmarking from Intel that’s always in need of independent review.

    But this is in fact Core Wars Episode 2, The Empire Glues 2 Death Stars together at a price sure to make a bean counter’s head go all planet Alderaan when the invoice arrives.

    P.S.

    I’m sure that there is a whole load of goodness for the consumer/gaming market to come from the Zen2 Micro-Arch on TSMC’s 7nm node but that’s not where the large Revenues and Hgher Gross Margins that AMD needs will be coming from. The consumer market is nice, do not get me wrong, but for CPUs in the consumer HEDT market, that’s where a Processor Business trys to some degree to make the best of those lower performing DIE binns that do not make the grade to be binned Epyc server grade parts, or Xeon for Intel’s CPU parts.

    Even with first generation Ryzen Desktop 8 core mainstream Parts they also came from Binned Zen/Zeppelin server DIEs so AMD was killing 3 birds(server, HEDT, and mainstream desktop CPUs) with one stone with that fist generation Zen/Zeppelin Die economy of scale. And that’s what has allowed AMD to really compete price/performance wise with Intel these last few years. There are now first generation 8 core Ryzen branded SKUs on sale for what Intel wants to charge for a quad core i5 series SKUs. As AMD has aready moved on to using a Zen+/Ryzen-2(2000 series) second generation consumer Die based 8 core/lower core count line of CPU SKUs(also selling at below MSRP Currently). And all this while Intel’s processor shortage is sure helping Intel’s gross margins to remain in the mid 60% range in the short term but in the long term Intel’s market share numbers will suffer.

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