AMD Next Gen CPU Leak

AMD’s next-gen CPU leak: 14nm, simultaneous multithreading, and DDR4 support

Ever since it became clear that AMD’s Carrizo would be a mobile update with a focus on energy efficiencyas opposed to raw performance, enthusiasts and investors have been hungry for details about the company’s upcoming CPUs in 2016. AMD has been tight-lipped on these projects, though we heard rumors of a combined x86-ARM initiative that was up and running as of early last year — but now, a handful of early rumors have begun to leak about the eventual capabilities of these new cores.

As with all rumors, take these with a substantial grain of salt — but here’s what Sweclockers.com is reporting to date. We’ll rate the rumors as they’re given on the site: According to the post, the new AMD Zen is:

Built on 14nm: For a chip launching in 2016, this seems highly likely. Jumping straight for 14nm won’t obviate the gap between AMD and Intel, but the company is currently building its FX chips on legacy 32nm SOI while its Kaveri and Carrizo are both 28nm bulk silicon. The double-node jump from 28nm to 14nm should give AMD the same benefits as a single-node process transition used to grant. Given the advantage of FinFET technology, we’d be surprised if the company went with anything else. The chips are also expected to be built at GlobalFoundries, which makes sense given AMD’s historic relationship with that company.

Utilize DDR4: Another highly likely rumor. By 2016, DDR4 should be starting to supplant DDR3 as the mainstream memory of choice for desktop systems. AMD might do a hybrid DDR3/DDR4 solution as it did in the past with the DDR2/DDR3 transition, or it might stick solely with the new interface.

Up to 95W: Moderately likely, moderately interesting. This suggests, if nothing else, that AMD wants to continue to compete in the enthusiast segment and possibly retake ground in the server and enterprise space. Nothing has been said about the graphics architecture baked on to the die, but opting for an up-to 95W TDP suggests that the company is giving itself headroom to fight it out with Intel once again.

Opt for Simultaneous multithreading as opposed to Cluster Multithreading: With Bulldozer, AMD opted for an arrangement called cluster multi-threading, or CMT. This is the strategy used by Bulldozer, in which a unified front end issues instructions to two separate integer pipelines. The idea behind the Bulldozer design was that AMD would gain the benefits of having two full integer pipelines but save die space and power consumption compared to building a conventional multi-core design.

Intel, in contrast, has long used simultaneous multithreading (SMT), which they call Hyper-Threading,  in which two instructions from different threads can be executed in the same clock cycle. In theory, AMD’s design could have given it an advantage, since each core contains a full set of execution units as opposed to SMT, where those resources are shared, but in practice Bulldozer’s low efficiencycrippled its scaling.

The rumor now is that AMD will include an SMT-style design with Zen. It’s entirely possible that the company will do this — Hyper-Threading is one example of SMT, but it’s not the only implementation — IBM, for example, uses SMT extensively in its POWER architectures. The reason I’m not willing to completely sign off on this rumor is that it’s a rumor that’s dogged AMD literally since Intel introduced Hyper-Threading 15 years ago.

The benefits of using SMT are always dependent on the underlying CPU architecture, but Intel has demonstrated that the technology is often good for a 15-20% performance increase in exchange for a minimal die penalty. If AMD can achieve similar results, the net effect will be quite positive.

The final rumor floating around is that the chip won’t actually make an appearance until the latter half of 2016. That, too, is entirely possible. GlobalFoundries’ decision to shift from its own 14nm-XM process to Samsung’s 14nm designs could have impacted both ramp and available capacity, and AMD has pointedly stated that it will transition to new architectures only when it makes financial sense to do so. The company may have opted for a more leisurely transition to 14nm in 2016, with the new architecture debuting only when GF has worked the kinks out of its roadmap.

We know HBM is coming, but it may not come to desktops or APUs immediately.

No information on performance or other chip capabilities is currently available, and the company has said nothing about the integrated GPU or possible use oftechnologies like HBM. The back half of 2016 would fit AMD’s timeline for possible APU integration of HBM — which means these new chips could be quite formidable if they fire on all thrusters out of the gate. During its conference call last week, AMD mostly dodged rumors about delays to its ARM products, noting that it had continued sampling them in house and was pleased with the response. Presumably the company’s partners remain under NDA — there are no published independent evaluations of these products to date.