Sizing Things Up: Specifications Compared

Thirty-two high-IPC cores in one package sounds promising. But how does the best ThunderX2 compare to what AMD, Qualcomm and Intel have to offer? In the table below we compare the high level specifications of several top server SKUs.

Comparison of Major Server SKUs Cavium
Centriq 2460
Xeon 8176
Xeon 6148
EPYC 7601
Process Technology TSMC
16 nm
10 nm
14 nm
14 nm
Global Foundries
14 nm
Cores 32
Ring bus
Ring bus
4 dies x 8 cores
Threads 128 48 56 40 64
Max. number of sockets 2 1 8 4 2
Base Frequency 2.2 GHz 2.2 GHz 2.2 GHz 2.4 GHz 2.2 GHz
Turbo Frequency 2.5 GHz 2.6 GHz 3.8 GHz 3.7 GHz 3.2 GHz
L3 Cache 32 MB 60 MB 38.5 MB 27.5 MB 8x8 MB
DRAM 8-Channel
PCIe 3.0 lanes 56 32 48 48 128
TDP 180W 120 W 165W 150W  180W
Price $1795 $1995 $8719 $3072 $4200

Astute readers will quickly remark that Intel's top of the line CPU is the Xeon Platinum 8180. However that SKU with its 205W TDP and $10k+ price tage is not comparable at all to any CPU in the list. We are already going out on a limb by including the 8176, which we feel belongs in this list of maximum core/thread count SKUs. In fact, as we will see further, Cavium positions the Cavium 9980 as "comparable" to the Xeon Platinum 8164, which is essentially the same part as the 8176 but with slightly lower clockspeeds.

However, it terms of performance per dollar, Cavium typically compares their flagship 9980 to the Intel Xeon Gold 6148, against which the pricing of Cavium's CPU is very aggressive. Many of Cavium's benchmarks claim that the fastest ThunderX2 is 30% to 40% ahead of the Xeon 6148, all the while Cavium's offering comes in at $1300 less. That aggressive pricing might explain the increasingly persistent rumors that Qualcomm is not going to enter the server market after all.

When looking at the table above, you can already see some important differences between the contenders. Intel seems to have the most advanced core topology and the highest turbo clockspeed. Meanwhile Qualcomm has the best chances when it comes to performance per watt, and has already published some benchmarking data that underlines this advantage.

Similar to AMD's EPYC, Cavium's ThunderX2 is likely to shine in the "sparse matrix" HPC market. This is thanks to its 33% greater theoretical memory bandwidth and a high core/thread count. However as we've seen in the case of AMD's design, EPYC's L3-cache is slow once you need data that is not in the local 8 MB cache slice. The ThunderX2, by comparison, is a lot more sophisticated with a dual ring architecture, which seems to be similar to the ring architecture of the Xeon v4 (Broadwell-EP). According to Cavium, this ring structure is able to offer up to 6 TB/s of bandwidth and is non-blocking.

This ring architecture is connected to Cavium's Coherent Processor Interconnect (CCPI2 - at the top of the picture), which runs at 600 Gb/sec. This interconnect links the two sockets/NUMA nodes. Also connected to the ring are the SoC's 56 PCIe 3.0 lanes, which Cavium allocates among 14 PCIe "controllers.". These 14 controllers can, in turn, be bifurcated down to x4 or x1 as you can see below.

SR-IOV, which is important for I/O virtualization (Xen and KVM), is also supported.

ThunderX2: Cavium Is Back Cavium's "New" Core: Vulcan
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  • Eris_Floralia - Wednesday, May 23, 2018 - link

    The L2$ for SKX should be 1MB (256+768KiB), 16-way.
  • Ryan Smith - Wednesday, May 23, 2018 - link

    Right you are. Thanks!
  • danjme - Wednesday, May 23, 2018 - link

  • Duncan Macdonald - Wednesday, May 23, 2018 - link

    The CPU may be much cheaper than the equivalent Intel CPU - however on the price of a complete server there would be almost no difference as the vast majority of the price of a server is in other items (RAM, storage, network, software etc). To take a significant share, the performance needs to be better than Intel CPUs on both a per thread and a per socket basis. Potential users will look at this CPU - see that it is not faster than Intel on a per thread basis and is also not X86-64 compatible and turn away with a shrug. A price difference of under 5% for a complete server is not enough to justify the risks of going from x86-64 to ARM.
  • BurntMyBacon - Thursday, May 24, 2018 - link

    Perhaps you are correct and the lack of per thread performance will not allow Cavium to take a "significant' share of the market from Intel. However, at this point, getting even a small amount of market penetration in the server market is a significant achievement for an ARM vendor. This processor doesn't need to take a "significant" share from Intel to be successful. It just needs to establish a solid foothold. Given the data, I think it has a good chance of succeeding in that.

    The bigger question in my mind is how Intel will respond. They already have the ability to make a many lite core accelerator as demonstrated by the Xeon Phi line. Will they bring this tech to their CPU lineup, create a new accelerator based on this tech to handle applications that use many light threads, create a new many small core CPU based on Goldmont Plus (or Tremont), or will they consider the ARM threat insignificant enough to ignore.
  • boeush - Wednesday, May 23, 2018 - link

    "(*) EPYC and Xeon E5 V4 are older results, run on Kernel 4.8 and a slightly older Java 1.8.0_131 instead of 1.8.0_161. Though we expect that the results would be very similar on kernel 4.13 and Java 1.8.0_161"

    What about Spectre/Meltdown mitigation patches? Were they in effect for 'older' results?
  • boeush - Wednesday, May 23, 2018 - link

    To elaborate: if those numbers really are from July 2017, then they don't reflect true performance in a server context any longer (servers are where Spectre/Meltdown patches would be applied most.). Since the performance impact of Spectre/Meltdown is greatest on speculative execution and memory loads/prefetching, I'd guess those super-aggressive memory subsystem performance numbers, as well as single thread IPC advantages that Intel's CPUs claim in your benchmarks, are not really entirely applicable any longer.
  • HStewart - Wednesday, May 23, 2018 - link

    Spectre has been proved to effect other CPU's than Intel and even effects ARM and AMD.,

    Image on this article states that this CPU supports Fully Out of Order execution. So with my understanding of Spectre that this CPU also has issues.

    To be honest I not sure how much the whole Spectre/Meltdown stuff is in this real world. It probably cause more harm in the computer industry than help.
  • Manch - Thursday, May 24, 2018 - link

    Commentor: Blah Blah Blah Spectre?
    HStewart: Shill Shill Shill must defend Intel by any means...
  • lmcd - Thursday, May 24, 2018 - link

    Commentor: reasonable position taken
    Manch: *banned for unreasonable, offensive comments*

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