The Current Intel offerings

Before we can discuss the ARM server SoCs, we want to look at what they are up against: the current low end Xeons. We have described the midrange Xeon E5s in great detail in earlier articles.

The Xeon E3-12xx v3 is nothing more than a Core i5/i7 "Haswell" dressed up as a server CPU: a quad-core die, 8MB L3 cache, and two DDR3 memory channels. You pay a small premium – a few tens of dollars – for enabling ECC and VT-d support. Motherboards for the Xeon E3 are also only a few tens of dollar more expensive than a typical desktop board, and prices are between the LGA-1150 and LGA-2011 enthusiast boards. The advantages are remote management courtesy of a BMC, mostly an Aspeed AST chip.

For the enthusiasts that are considering a Xeon E3, the server chip has also disadvantages over it's desktop siblings. First of all, the boards consume quite a bit more power while in sleep state: 4-6W instead of the typical <1W of the desktop boards. The reason is that server boards come with a BMC and that these boards are supposed to be running 24/7 and not sleeping. So less time is invested in reducing the power usage in sleep mode: for example the voltage regulators are chosen to live long. Also, these boards are much more picky when it comes to DIMMs and expansions cards meaning that users have to check the hardware compatibility lists for the motherboard itself.

Back to the server world, the main advantage of the Xeon E3 is the single-threaded performance. The Xeon E3-1280 v3 runs the Haswell cores at 3.6GHz base clock and can boost to 4GHz. There are also affordable LP (Low Power) 25W TDP versions available, e.g. the Xeon E3-1230L v3 (1.8GHz up to 2.8GHz ) and E3-1240L v3 (2GHz up to 3GHz). These chips seemed to be in very limited supply when they were announced and were very hard to find last year. Luckily, they have been available in greater quantities since Q2 2014. It also worth noting that the Xeon E3 needs a C220 chipset (C222/224/226) for SATA, USB, and Ethernet, which adds 0.7W (idle) to 4.1W (TDP).

The weak points are the limited memory channels (bandwidth), the fact that Xeon E3 server is limited to eight threads, and the very limited (for a server) 32GB RAM capacity (4 Slots x 8 DIMMs). Intelligent Memory or I'M is one of the vendors that is trying to change this. Unfortunately their 16GB DIMMs will only work with the Atom C2000, leading to the weird situation that the Atom C2000 supports more memory than the more powerful Xeon E3. We'll show you our test results of what this means soon.

The Atom C2000 is Intel's server SoC with a power envelope ranging from 6W (dual-core at 1.7GHz) to 20W (octal-core at 2.4GHz). USB 2.0, Ethernet, SATA3, SATA2 and the rest (IO APIC, UART, LPC) are all integrated on the die, together with four pairs of Silvermont Cores sharing 1MB L2 cache. The Silvermont architecture should process about 50% more instructions per clock cycle than previous Atoms due an improved branch prediction, the loop stream detector (like the LSD in Sandy Bridge) and out-of-order execution. However the Atom micro architecture is still a lot simpler than Haswell.

Silvermont has much smaller buffers (for example, the load buffer only has 10 entries, where Haswell has 72!), no memory disambiguation, it executes x86 instructions (and not RISC-like micro-ops), and it can process at the most two integer and two floating point instructions, with a maximum of two instructions per cycle sustained. The Haswell architecture can process and sustain up to five instructions with "ideal" software. AES-NI and SSE 4.2 instructions are available with the C2000, but AVX instructions are not.

The advantages of the Atom C2000 are the low power and high integration -- no additional chip is required. The disadvantages are the relatively low single-threaded performance and the fact that the power management is not as advanced as the Haswell architecture. Intel also wants a lot of money for this SoC: up to $171 for the Atom C2750. The combination of an Atom C2000 and the FCBGA11 motherboard can quickly surpass $300 which is pretty high compared to the Xeon E3.

ARM, Micro and Scale-out Servers The ARM Based Challengers: AppliedMicro
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  • JohanAnandtech - Tuesday, December 16, 2014 - link

    Did you miss this page?
    http://www.anandtech.com/show/8776/arm-challinging...

    The software ecosystem is developing...there is no indication that this will stop soon.
    Reply
  • Kevin G - Wednesday, December 17, 2014 - link

    The LAMP stack is there and can easily give ARM a foot hold. Scaling up they'll need vendors like Oracle to port key applications. ARM will also need to enhance there RAS to be production capable with that software. Reply
  • Samus - Tuesday, December 16, 2014 - link

    Johan,

    You need to review the compatibility of the Xeon E3's. They actually work in just about any Intel 80 or 90-series board. I have an E3-1230v3 in an Asus ITX H87 on the PC I'm currently typing on.

    A C220 chipset is NOT required.
    Reply
  • JohanAnandtech - Tuesday, December 16, 2014 - link

    you are right :-).

    By "Xeon E3 needs C220" I meant that you need to add that part to calculate the power consumption per node. And the E3 needs it to support ECC RAM.
    Reply
  • eanazag - Tuesday, December 16, 2014 - link

    Ubuntu's ARM version OS is a big deal. I believe the fact that MS had been dragging on with supporting RT was in fact to have something to port to the server side. Even though RT is mostly a dud at first, it could still be sensible and sell in a server config.

    I'm waiting for AMD to finally sell the ARM chip in the channel so I can throw a mobo with it together. If it has 10GbE I would be all over it.
    Reply
  • rootheday3 - Tuesday, December 16, 2014 - link

    Intel also has Rangeley soc which includes crypto block for comms usage Reply
  • wintermute000 - Tuesday, December 16, 2014 - link

    "What if I need massive amounts of memory but moderate processing power? The Xeon E3 only supports 32GB."

    Thousands of techs labbing away @ home nod sagely in agreement. Right now our choices are to scale horizontally or live with loud jet-engine ex-enterprise gear, because I can't get 64gb of RAM into a whitebox.
    Reply
  • wintermute000 - Tuesday, December 16, 2014 - link

    Clarification: a whitebox that I can afford i.e. not a Xeon E5. lol Reply
  • beginner99 - Wednesday, December 17, 2014 - link

    What kind of servers use tons of RAM and little processing power? Right, memcached and similar stuff. But let's be honest. That is still a niche market given the total server market. Most servers are just standard multipurpose servers running some company internal low-traffic (web) application. They don't need memcached. Memcached is for huge internet deployments and let's be honest that in itself is niche.

    I work in a 10'000 people company and I would bet you $1000 we have 0 memcached servers. I don't really know except for the lack of performance in core apps and the questionable competency of our IT.
    Reply
  • bobbozzo - Wednesday, December 17, 2014 - link

    VM servers.
    And ZFS-filesystem storage (NAS/SAN) servers. e.g. FreeNAS. Add much more RAM if using DeDup.
    Reply

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