AMD Zen Architecture and Performance Preview
Gunning for Broadwell-E
As I walked away from the St. Regis in downtown San Francisco tonight, I found myself wandering through the streets towards my hotel with something unique in tow. It was a smile. I was smiling, thinking about what AMD had just demonstrated and showed at its latest Zen processor reveal. The importance of this product launch can literally not be overstated for a company struggling to find a foothold to hang on to in a market that it once had a definitive lead. It’s been many years since I left a conference call, or a meeting, or a press conference feeling genuinely hopefully and enthusiastic about what AMD has shown me. Tonight I had that.
AMD’s CEO Lisa Su, and CTO Mark Papermaster, took stage down the street from the Intel Developer Forum to roll out a handful of new architectural details about the Zen architecture while also showing the first performance results comparing it to competing parts from Intel. The crowd in attendance, a mix of media and analysts, were impressed. The feeling was palpable in the room.
It’s late as I write this, and while there are some interesting architecture details to discuss, I think it is in everyone’s best interest that we touch on them lightly for now, and instead refocus on the deep-dive once the Hot Chips information comes out early next week. What you really want to know is clear: can Zen make Intel work again? Can Zen make that $1700 price tag on the Broadwell-E 6950X seem even more ludicrous? Yes.
The Zen Architecture
Much of what was discussed from the Zen architecture is a re-release of what has been out in recent months. This is a completely new, from the ground up, microarchitecture and not a revamp of the aging Bulldozer design. It integrated SMT (simultaneous multi-threading), a first for an AMD CPU, to better take efficient advantage of a longer pipeline. Intel has had HyperThreading for a long time now and AMD is finally joining the fold. A high bandwidth and low latency caching system is used to “feed the beast” as Papermaster put it and utilizing 14nm process technology (starting at Global Foundries) gives efficiency, and scaling a significant bump while enabling AMD to scale from notebooks to desktops to servers with the same architecture.
By far the most impressive claim from AMD thus far was that of a 40% increase in IPC over previous AMD designs. That’s a HUGE claim and is key to the success or failure of Zen. AMD proved to me today that the claims are real and that we will see the immediate impact of that architecture bump from day one.
Press was told of a handful of high level changes to the new architecture as well. Branch prediction gets a complete overhaul. This marks the first AMD processor to have a micro-op cache. Wider execution width with broader instruction schedulers are integrated, all of which adds up to much higher instruction level parallelism to improve single threaded performance.
Performance improvements aside, throughput and efficiency go up with Zen as well. AMD has integrated an 8MB L3 cache and improved prefetching for up 5x the cache bandwidth available per core on the CPU. SMT makes sure the pipeline stays full to prevent “bubbles” that introduce latency and lower efficiency while region-specific power gating means that we’ll see Zen in notebooks as well as enterprise servers in 2017. It truly is an impressive design from AMD.
Summit Ridge, the enthusiast platform that will be the first product available with Zen, is based on the AM4 platform and processors will go up to 8-cores and 16-threads. DDR4 memory support is included, PCI Express 3.0 and what AMD calls “next-gen” IO – I would expect a quick leap forward for AMD to catch up on things like NVMe and Thunderbolt.
The Real Deal – Zen Performance
As part of today’s reveal, AMD is showing the first true comparison between Zen and Intel processors. Sure, AMD showed a Zen-powered system running the upcoming Deus Ex running at 4K with a system powered by the Fury X, but the really impressive results where shown when comparing Zen to a Broadwell-E platform.
Using Blender to measure the performance of a rendering workload (a Zen CPU mockup of course), AMD ran an 8-core / 16-thread Zen processor at 3.0 GHz against an 8-core / 16-thread Broadwell-E processor at 3.0 GHz (likely a fixed clocked Core i7-6900K). The point of the demonstration was to showcase the IPC improvements of Zen and it worked: the render completed on the Zen platform a second or two faster than it did on the Intel Broadwell-E system.
Not much to look at, but Zen on the left, Broadwell-E on the right...
Of course there are lots of caveats: we didn’t setup the systems, I don’t know for sure that GPUs weren’t involved, we don’t know the final clocks of the Zen processors releasing in early 2017, etc. But I took two things away from the demonstration that are very important.
- The IPC of Zen is on-par or better than Broadwell.
- Zen will scale higher than 3.0 GHz in 8-core configurations.
AMD obviously didn’t state what specific SKUs were going to launch with the Zen architecture, what clock speeds they would run at, or even what TDPs they were targeting. Instead we were left with a vague but understandable remark of “comparable TDPs to Broadwell-E”.
Pricing? Overclocking? We’ll just have to wait a bit longer for that kind of information.
There is clearly a lot more for AMD to share about Zen but the announcement and showcase made this week with the early prototype products have solidified for me the capability and promise of this new microarchitecture. We have asked for, and needed, as an industry, a competitor to Intel in the enthusiast CPU space – something we haven’t legitimately had since the Athlon X2 days. Zen is what we have been pining over, what gamers and consumers have needed.
AMD’s processor stars might finally be aligning for a product that combines performance, efficiency and scalability at the right time. I’m ready for it –are you?