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Officials with Advanced Micro Devices went to the Hot Chips 2016 show to preach the benefits of “Zen.”
Company executives last week were in San Francisco at a hotel not too far from where larger rival Intel was holding its annual developer conference to demonstrate the new Zen microarchitecture, which will form the basis of future processors that will power everything from fanless notebooks to supercomputers for high-performance computing (HPC) environments.
AMD is expecting the Zen core, which is slated to begin appearing in high-end desktop PCs later this year and into 2017 and in servers in the second quarter, to fuel its push to become competitive again in the client and data center spaces. President and CEO Lisa Su and other executives introduced Zen in May 2015 as the cornerstone of the company’s restructured product road map, and now have begun to show the industry what the new microarchitecture can offer in terms of performance and power efficiency.
That brought Mike Clark, senior fellow at AMD, to Hot Chips in Cupertino, California, Aug. 23 to outline what company engineers did to build the new microarchitecture, which now delivers 40 percent better instructions-per-clock performance over the company’s current Excavator core while keeping a lid on power consumption.
In an interview with eWEEK before the presentation, Clark and Sam Naffziger, AMD corporate fellow, talked about the challenges presented to them and other engineers four years ago when they were tasked with overhauling the AMD microarchitecture to create a core that will enable the company to once again compete in an increasingly crowded processor space. Not only did that space include traditional rival Intel, but also newer competitors in ARM and its array of manufacturing partners such as Qualcomm and Samsung, not to mention a revived IBM and its new OpenPower effort.
The key from the beginning was achieving the performance gains while keeping power consumption down, Clark said. With Zen, energy efficiency was going to be just as important as performance.
“We had to reset the architecture,” he said. “We focused on the power of the architecture from the beginning.”
With Zen, AMD officials are hoping to make the same sort of impact on the market that the company made more than a decade ago, when it was the first vendor to offer 64-bit computing in the x86 architecture and then dual-core processors. The innovations enabled AMD to capture about a quarter of the server market, but Intel’s design and manufacturing prowess, combined with missteps by AMD, conspired to knock away at the market share. Intel now sells more than 90 percent of all server chips worldwide.
Such microarchitectures as “Bulldozer” and “Excavator” were disappointments, and AMD officials decided that what the company needed was a complete reworking of the core design. Naffziger said that AMD for several years had been able to depend on innovation in such areas as GPUs and systems-on-a-chip (SoCs) to keep moving forward, even with cores that he said were “not as competitive.” With the advancements in Zen, that problem has been solved.
“Now we are getting the final element that we had been missing in a very competitive core,” Naffziger told eWEEK.
The Zen cores come with a broad range of enhancements that target both performance and power efficiency, including running two threads per core, a large operational cache, faster Layer 2 and L3 cache and improved L1 and L2 prefetcher. Engineers also reworked the CPU’s cache, essentially building a bigger engine, Clark said. Zen offers almost twice the bandwidth in the L1 and L2 cache than Excavator and up to five times the bandwidth for the L3 cache.
AMD also embraced simultaneous multithreading—a technology similar to Intel’s Hyper-Threading—for improved performance and improved the branch prediction technology. It used a 14nm FinFET manufacturing process for better performance and efficiency.
AMD Lays Out the Argument for Zen at Hot Chips Show
As a result, AMD was able to hit the ambitious performance and efficiency goals its officials first talked about 15 months ago. The company demonstrated those capabilities during the event for analysts and journalists a week ago, and are expecting the numbers to follow through when the chips start appearing in systems later this year and as they ramp in 2017. Officials also said that tests found the performance of the Zen chips were competitive with—and at times outperformed—Intel’s new “Broadwell-E” chips.
The first chips scheduled to hit the market will be “Summit Ridge” CPUs for high-end desktops, which will offer eight cores and 16 threads and will use the same AM4 socket as the company’s latest seventh-generation A-Series chips announced this summer. Those chips will be followed by the 32-core, 64-thread “Naples,” which is set to begin shipping in servers in the second quarter next year, followed by Zen-based notebooks in the second half of 2017. More CPUs and accelerated-processing units (APUs)—which include both the CPU and GPU on the same piece of silicon—will ship after that.
Clark said Zen isn’t the first chip he’s helped design from scratch—he was part of the team that developed AMD’s K5 processor almost two decades ago. But it’s never easy.
“For me, it wasn’t the first time, but you don’t do it often because it is so daunting,” he said. “It’s going to take a lot of [effort] and time. … It comes with a lot of risk.”
It also came as AMD was reworking other parts of the company including its graphics business, where engineers were developing the new Polaris GPU architecture introduced earlier this year. However, such efforts also helped contribute to the work on Zen. For example, the Polaris architecture also is built on a 14nm FinFET process, which gave Zen engineers data to learn from.
Overall, the result is what Clark was hoping for when the work on the new microarchitecture began all those years ago with a focus on both performance and power efficiency.
“As the lead [on the core development], I picked ‘Zen’ as the [codename] because zen is a balance,” he said. “We needed to balance the whole thing to make it work.”