A closer look at IBM’s Power8 and OpenPower Foundation: Taking aim at Intel’s x86 server monopoly

IBM has taken the wraps off the first servers that are driven by its monstrously powerful Power8 CPUs. With more than 4 billion transistors, packed into a stupidly large 650-square-millimetre die built on IBM's new 22nm SOI process, the 12-core (96-thread) Power8 CPU is one of the largest and probably the most powerful CPU ever built.

In a separate move, IBM is opening up the entire Power8 architecture and technical documentation through the OpenPower Foundation, allowing third parties to make Power-based chips (much like ARM's licensing model), and to allow for the creation of specialised coprocessors (GPUs, FPGAs, etc) that link directly into the CPU's memory space using IBM's new CAPI interface.

You will not be surprised to hear that Nvidia, Samsung, and Google – three huge players among hundreds more who are beholden to Intel's server monopoly – are core members of the OpenPower Foundation. The Power8 CPU and the OpenPower Foundation are the cornerstones of a very big, well-orchestrated plan to finally put an end to x86's reign, and place a fairer, more powerful architecture at the head of the server table.

First, we should talk about the new Power8 chip. There are 12 CPU cores, each with 512KB of L2 SRAM and 8MB of L3 EDRAM, for a total of 6MB L2 and 96MB L3 cache respectively. There is then a further 230GB/sec of bandwidth to 1TB of DRAM. Whereas each Intel Xeon core is capable of two-way simultaneous threading, and Power7+ cores can do four threads, Power8 ups the ante to eight simultaneous threads (SMT).

As you'd expect, other parts of the chip have been similarly expanded to cater for the Power8's massive parallelism: There are eight decoders (up from 6), six dispatches per clock cycle, a doubling of load units (4), the data cache can now process four 128-bit transactions per cycle, and the bus width between the L2 and data cache is now 512 bits.

Take a look at the block diagram below and be awed by its massive parallelism and throughput.

We expect the Power8 will eventually be capable of clock speeds of around 4.5GHz, with a TDP in the region of 250 watts. At this speed, the Power8 CPU will be around 60 per cent faster than the Power7+ in single-threaded applications, and more than twice as fast in multithreaded tasks. In certain cases, IBM says the Power8 is capable of analysing Big Data workloads between 50 and 1,000 times faster than comparable x86 systems (the same amount of RAM, the same number of cores).

Compared to its competitors (Power 7+, the Oracle Sparc T5, the Intel Xeon), the Power8 has anywhere between two and three times more processing power per socket. This is mostly due to the massive thread count (96 versus 30 for the latest 15-core E7-8890 v2 Xeon), and utterly insane memory bandwidth (230GB/sec versus 85GB/sec). In terms of performance per watt, though, the Xeon (~150W TDP) is probably just ahead of the Power8 – but in general, when you're talking servers, power consumption generally plays second fiddle to performance density (how many gigaflops you can squeeze out of a single server).

Beyond raw SPECint and SPECfp performance, Power8 also introduces CAPI (Coherence Attach Processor Interface). CAPI is a direct link into the CPU, allowing peripherals and coprocessors to communicate directly with the CPU, bypassing (substantial) operating system and driver overheads. CAPI is similar to Intel's QPI, but where QPI is closed and proprietary, IBM is opening up CAPI to third parties. IBM's Power Systems CTO, Satya Sharma, told me in an interview that in the case of flash memory attached via CAPI the overhead is reduced by a factor of 20. More importantly, though, CAPI can be used to attach coprocessors – GPUs, FPGAs – directly to the Power8 CPU for some truly insane workload-specific performance boosts. It is due to these CAPI-attached coprocessors that a Power8 system can be 1,000 times faster than a comparable x86 system.

Which brings us neatly onto the OpenPower Foundation...

The OpenPower Foundation

While the Power8 chip is veritably beastly, it will take a lot more than a fancy piece of hardware to dislodge Intel x86 as the undisputed king of servers (Intel chips currently power somewhere in the region of 95 per cent of all servers.) What IBM needs is a full top-to-bottom Power architecture stack, from first-party and third-party hardware, through to a broad, healthy ISV (independent software vendor) ecosystem. This is where the OpenPower Foundation comes in.

Basically, IBM is making the Power8 architecture and detailed technical documentation open to members of the Foundation. Currently, the foundation consists of Altera, Google, Nvidia, Micron, Samsung, Tyan, ZTE, and others. Each of these members will use the Power documentation in different ways. Altera is developing FPGAs that connect directly into the Power8 chip via CAPI, to provide stupendous speed-ups for specific tasks. Tyan, with help from Google, will create third-party motherboards that are compatible with the Power8 chip, with the goal of producing cheap, Power8-based machines for Internet-scale server farms. Nvidia, like Altera, will develop a Tesla-like GPU coprocessor that connects directly to the CPU via CAPI. Suzhou will license the Power architecture to make its own Power8-compatible chips for China's domestic server market.

Taking down Intel

The hope is that by cultivating a broad hardware and software ecosystem, Power will be able to challenge Intel in the server space. IBM wants to be the ARM of servers, basically: In much the same way that ARM's open architecture and licensing model allowed it to squash Intel in the mobile and embedded spaces, IBM wants to do the same thing in servers.

Usually I would say that it's a fool's errand to challenge Intel, but if anyone can do it, it's IBM. There is a lot of antipathy towards Intel and the strategies it has used to dismantle everyone and everything that has threatened to disrupt its dominion over the computing industry. Server vendors (IBM, HP, Dell) and Internet-scale service providers (Google, Facebook) use x86 chips, but only because Intel has ensured that there's no other viable option. I don't think there's a single company that doesn't want to get out from underneath the choking heft of Intel x86 – and now, at long last, IBM might be offering a way out. If the surge in mobile computing has taught us anything it's that Intel isn't unbeatable – that there's a chink in its armour that IBM and the rest of the OpenPower Foundation think they can exploit. "We are entering some new spaces," Sharma told me. "It's a transformational event for Power. It's going to take Power to new spaces we haven't gone before."

IBM has also announced that Canonical's Ubuntu Server will be available for all Power8-based systems, and that it will continue to invest in Linux (IBM/Power is historically Unix-focused, not Linux). "Now is the time to expand into the Linux space," Sharma said as our interview was wrapping up. "Ubuntu is now one of the primary targets for Power."

The first Power8 servers will be available from 10 June, with a range of 1 and 2-socket 2U and 4U models. The Power S812L and Power S822L (both 2U) will exclusively run Linux. The flagship of the Power8 line is the Power S824, a 4U design with two CPU sockets, maxing out at 24 cores (192 threads) and 1TB of RAM. The low-end Linux-powered S812L server starts at $8,000 (£4,800). (IBM wouldn't tell us the exact pricing of a standalone Power8 CPU, but it's probably in the region of $5,000, which is £3,000).

Image Credit: The Linley Group