While ARM started in desktops many years ago, it's mainstay is now in mobile devices. However, it is aiming at higher ground, including wrestling away a part of server market from the X86 vendors. What is Intel doing to keep them at bay, and what impact will it have?
Anyone of the old guard still remembers the 1985 Acorn Risc Machine, or, in shortform, ARM? From my teenage days, it was a memory of an exciting new processor architecture, completely different from its contemporary complex instruction set competitors – just like in modern buildings, simplicity was the answer, and complexity was left to the compilers. The first ARM was 32-bit, just like its follow-ons 26 years ago now.
After staging a grand revival through the smartphone and tablet markets, and becoming the definite No. 2 CPU platform in the world, ARM has now set its sights higher, to the mainstream mobile, desktop and yes, even server markets. And that's where it hits the X86 leaders, Intel and AMD, spot on.
Now, ARM has no software base to speak of in the server field, and its architecture not only is still 32-bit, but also lacks all those error correction, reliability and durability features expected in servers. However, the application specific 'green' micro servers, used just for serving web page accesses, don't need any of these. They just require the ability to put hundreds of energy-saving simple CPUs in a single rack, each serving a group of web requests in a small local memory, 2 GB – the 32-bit direct addressing limit after I/O space is taken – being more than enough for it.
This a relatively small part of server market, and a low-margin one, an equivalent of generic corporate desktop in the PC market. But an entry is still an entry, very worthy for ARM CPU vendors to get a foothold before they are ready for more, once the Windows 8 and, then, the 64-bit ARM arrive.
So, the danger is there – remember that X86 core consumes more power and die size than an equivalent performance RISC, so it needs to be compensated through system design. On the other hand, Atom is 64-bit from the start, keep in mind – an enormous benefit when handling any sort of shared memory mapping between hundreds of processors in a single server, something impossible for ARM for another 2 years or so. Not to mention all the X86 software support built over the years, something ARM will not have in foreseeable future.
And that's where Intel's 2012 answer to ARM comes, in the form of 'Bordenville' Atom microserver platform around the 'Centerton' chip, optimised from ground up for this segment, especially at the system level. The quadruple density compared to even the lowest voltage Xeon, with over 2,000 processors in one rack, and the simplest ever system design of any X86 processor, are aimed at creating a formidable wall against the ARM entry into this market.
The Centerton chip itself is a simple dual-core 32 nm 64-bit CPU. It contains just two 'Saltwell' multithreaded 1.6 GHz Atom cores with 512 KB L2 cache each, a single-channel DDR3-1333 ECC low voltage memory controller for up to 8 GB on a single SO-DIMM, and 8 PCIe v2 lanes, with legacy I/O and SMbus included on-die as well. This removes the need for any sort of chipset. Simply, just use PCIe v2 lanes to attach what you really wish, like a Gigabit Ethernet, storage controllers like SAS, InfiniBand or even one of those PLX PCIe v2 switches to let multiple processors talk to each other directly over PCIe itself at ultra low latency!
With this kind of compact footprint, we are talking about just 5W to 8W total TDP for the whole system on a chip (SoC), and an enormously efficient footprint with CPU modules just about the size of a credit card! And this is a chip with full memory RAS features including scrubbing; with full virtualisation implemented as well, and 64-bit address space.
What impact would this launch have? Well, it hits ARM in the two weakest spots: lack of 64-bitness and software support. The extra server features like RAS and virtualisation, which ARM takes time to implement, are also native here. And, despite the complexity of the clumsy x86 core, the overall power consumption per node will be similar to the best ARMs in class – and this is a 32 nm chip, mind you. Also, for dense 'green' supercomputing, this chip may have some allure, as it can even allow tight interconnecting of many of them together via PCIe switches on local boards, then further via InfiniBand or Ethernet.
On the other hand, the vendors like HP and Dell are anyway waiting to diversify their offerings a bit, and not just depend on X86. HP is already promoting such microservers, and ARM will have some foothold, like it or not. Either way, the 2012 microserver market will be the first battle of the larger upcoming high end market war between X86 and ARM.