ARM Challenging Intel in the Server Market: An Overview
by Johan De Gelas on December 16, 2014 10:00 AM ESTRISC vs. CISC Revisited
The RISC vs. CISC discussion is never ending. It started as soon as the first RISC CPUs entered the market in the mid eighties. Just six years ago, Anand reported that AMD's CTO, Fred Weber was claiming:
Fred said that the overhead of maintaining x86 compatibility was negligible, at the time around 10% of the die was the x86 decoder and that percentage would only shrink over time.
Just like Intel today, AMD claimed that the overhead of the complex x86 ISA was dwindling fast as the transistor budget grew exponentially with Moore's law. But the thing to remember is that high ranking managers will always make statements that fit their current strategy and vision. Most of the time there is some truth in it, but the subtleties and nuances of the story are the first victims in press releases and statements.
Now in 2014, it is good to put an end to all this discussion: the ISA is not a game changer, but it matters! AMD is now in a very good position to judge as it will develop x86 and ARM CPUs by the same team, lead by the same CPU architecture veteran. We listened carefully to what Jim Keller, the head of the AMD CPU architect team, had to say in the 4th minute of this YouTube video:
"The big fundamental thing is that ARMv8 ISA has more registers (32), a three operand ISA, and spends less transistors on decoding and dealing with the complexities of x86. That allows us to spend more transistors on performance... ARM gives us some inherent architectural efficiency."
You can debate until you drop, but there is no denying that the x86 ISA requires more pipeline stages and thus transistors to decode than any decent RISC ISA. As x86 instructions are variable length, fetching instructions is less efficient and requires more transistors. The instruction cache is also larger as you need to store pre-decode information. The back-end might deal with RISC-like micro-ops but as the end result must adhere to rules of the x86 ISA, thus transistors are spent on exception handling and condition codes.
It's true that the percentage of transistors spent on decoding has dwindled over the years. But the number of cores has increased significantly. As a result, the x86 tax is not imaginary.
Hardware Accelerators
While we feel that the ARMv8 ISA is definitely a competitive advantage for the ARM server SoCs, the hardware accelerators are a big mystery: we have no idea how large the performance or power advantage is in real software. It might be spectacular or it might be just another "offload works only in the rare case where all these conditions are met". Nevertheless, it is interesting to see how the ARM server SoC has many different integrated accelerators.
Most of them are the usual IPSec, TCP offloading engines, and Cryptographic accelerators. It will be interesting to see if the ARM ecosystem can offer more specialized devices that can really outperform the typical Intel offerings.
One IP block that got my attention was the the Regex accelerators of Cavium. Regular expression accelerators are specialized in pattern recognition and can be very useful for search engines, network security, and data analytics. That seems exactly what we need in the current killer apps. But the devil is in the details: it will need software support, and preferably on a wide scale.
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beginner99 - Tuesday, December 16, 2014 - link
Agree. I just don't see it. What wasn't mentioned or I might have missed is Intels turbo technology. Does ARM have anything similar? Single-threaded performance matters. If a websites takes double the time to be built by the server the user can notice this. And given complexity of modern web sites this is IMHO a real issue. Latency or "service time" is greatly affected by single-threaded performance. That's why visualization is great. Put tons of low-usage stuff on the same physical server and yet each request profits from the single-threaded performance.Now these ARM guys are targeting this high single-threaded performance but why would any company change? Whole software stack would have to change as well at don't forget the software usually cost way, way more than the hardware it runs on. So if you save 10% on the SOC you maybe save less than 1% on the total BOM including software. They can't win on price and on performance/watt Intel still hast best process. So no i don' see it except for niche markets like these Mips SOCs from cavium.
Ratman6161 - Wednesday, December 17, 2014 - link
"Xeon performance at ridiculous prices" I just don't get the "ridiculous prices" comment. To me, it seems like hardware these days is so cheap they are practically giving it away. I remember in the days of NT 4.0 Servers we paid $40K each for dual socket Dell systems with 16 GB Ram.A few years later we were doing Windows 2000 Server on Dell 2850's that were less than half the price.
Then in 2007 we went the VMWare route on Dell 2950's where the price actually went up to $23K but we were getting dual sockets/8 cores and 32GB of RAM so they made the $40K servers we bought years before look like toys.
Four years later we got R-710's that were dual socket/12 cores and 64GB or RAM and made the $23K 2950's look like clunkers but the price was once again almost half at about $12K.
Today we are looking at replacing the R-710's with the latest generation which will be even more cores and more RAM for about the same price.
So to me, the prices don't seem ridiculous at all. The servers themselves now make up only a fraction of our hardware costs with the expensive items being SAN storage. But that too is a lot cheaper. We are looking at going from our two SANS with 4GB fiber channel connections to a single SAN with 10GB Ethernet and more storage than the two old units combined...but still costing less than the old SANs did for just one. So prices there are expensive but less than half of what we paid in 2007 for more storage.
The real costs in the environment are in Software licensing and not I'm not talking about Microsoft or even VMware. Licensing those products are chump change compared to the Enterprise Software crooks...that's where the real costs are. The infrastructure of servers, storage and "plumbing" sorts of software like Windows Server and VMWare are cheap in comparison.
mrdude - Tuesday, December 16, 2014 - link
Great article, JohanI think the last page really describes why so many people, myself included, feel that ARM servers/vendors have a very good chance of entrenching themselves in the market. Server workloads are more complex and varied today than they ever have been in the past and it isn't high volume either: the Facebook example is a good one. These companies buy hardware by the truckload and can benefit immensely from customization that Intel may not have on offer.
To add to that, what wasn't mentioned is that ARM, due to its 'license everything' business model, provides these same companies the opportunity to buy ready-made bits of uArch and, with a significantly smaller investment, build them own as-close-to-ideal SoC/CPU/co-processor that they need.
Competition is a great thing for everyone.
JohanAnandtech - Tuesday, December 16, 2014 - link
True. Although it seems that only AMD really went for the "license almost everything" model of ARM.mrdude - Tuesday, December 16, 2014 - link
Yep. And that's likely due to the budget/timing constraints. I think they were gunning for the 'first to market' branding but they couldn't meet their own timelines. Something of a trend with that company. I'm curious as to why we haven't heard a peep from AMD or partners regarding performance or perf-per-watt. Iirc, we were supposed to see Seattle boards in Q3 of 2014.I also feel like ARM isn't going to stop at the interconnect. There's still quite a bit of opportunity for them to expand in this market.
cjs150 - Tuesday, December 16, 2014 - link
Ultimately, my interest in servers is limited but I would like a simple home server that would tie all my computers, NAS, tablets and the other bits and bobs that a geek household has.witeken - Tuesday, December 16, 2014 - link
Who's interested in Intel's data center strategy, can watch Diane Bryant's recent presentation (including PDF): http://intelstudios.edgesuite.net/im/2014/live_im.... The Q&A from 2013 also has some comments about ARM servers: http://intelstudios.edgesuite.net/im/2013/live_im....Kevin G - Tuesday, December 16, 2014 - link
"Now combine this with the fact that Windows on Alpha was available." - Except that Windows NT was available for Alpha. There was a beta for Windows 2000 in both 32 bit and 64 bit flavors for the curious.I disagree with the reason why Intel beat the RISC players. Two of the big players were defeated by corporate politics: Alpha and PA-RISC were under the control of HP who was planning to migrate to Itanium. That leaves POWER, SPARC, MIPs and Intel's own Itanium architecture at the turn of the millennium. Of those, POWER and SPARC are still around as they continue to execute. So the only two victims that can be claimed by better execution is MIPs and Intel's own Itanium.
While IBM and Oracle are still executing on hardware, the Unix market as a whole has decreased in size as a whole. The software side isn't as strong as it'd use to be. Linux has risen and proven itself to be a strong competitor to the traditional Unix distribution. Open source software has emerged to fill many of the roles Unix platforms were used to. Further more, many of these applications like Hadoop and Casandra are designed to be clustered and tolerate node failures. No need to spend extra money on big iron hardware if the software doesn't need that level of RAS for uptime. The general lower cost of Linux and open source software (though they're not free due to the need for support) combined with furhter tightening of budgets during the great recession has made many businesses reconsider their Unix platforms.
JohanAnandtech - Tuesday, December 16, 2014 - link
My main argument was that the RISC market was fragmented, and not comparable to what the x86 market is now (Intel dominating with a very large software base).While I agree with many of your points, you can not say that SPARC is not a victim. In 90ies, Sun had a very broad product range from entry-level workstation to high-end server. The same is true for the Power CPUs.
Kevin G - Wednesday, December 17, 2014 - link
The RISC market was fragmented on both hardware and software. The greatest example of this would be HP that had HPUX, Tru64, OpenVMS, and Nonstop as operating system and tried to get them all migrated to a common hardware platform: Itanium. How each platform handled backwards compatibility with their RISC roots was different (and Tru64 was killed in favor of HPUX).The midrange RISC workstation suffered the same fate as the dual socket x86 workstation market: good enough hardware and software existed for less. The race to 1Ghz between Intel and AMD cut out the performance advantage RISC platforms carried. Not to say that the RISC a chips didn't improve performance but vendors never took steps to improve their price. Window 2000 and the rise of Linux early in the 2000's gave x86 a software price advantage too while having good enough reliability.
Sun's hardware business did suffer some horrible delays which helped lead the company into Oracle's acquisition. Notably was the Rock chip which featured out-of-order execution but also out-of-order instruction retirement. Sun was never able to validate any prototype silicon and ship it to customers.