AMD Zen Microarchitecture: Dual Schedulers, Micro-Op Cache and Memory Hierarchy Revealed
by Ian Cutress on August 18, 2016 9:00 AM ESTSimultaneous Multi-Threading
On Zen, each core will be able to support two threads in what is called ‘simulatenous multi-threading’. Intel has supported their version of SMT for a number of years, and other CPU manufacturers like IBM support up to 8 threads per core on their POWER8 platform designs. Building a core to be able to use multiple threads can be tough, as it requires a lot of resources to make sure that the threads do not block each other by consuming all the cache and buffers in play. But AMD will equip Zen with SMT which means we will see 8C/16T parts hitting the market.
Unlike Bulldozer, where having a shared FP unit between two threads was an issue for floating point performance, Zen’s design is more akin to Intel’s in that each thread will appear as an independent core and there is not that resource limitation that BD had. With sufficient resources, SMT will allow the core instructions per clock to improve, however it will be interesting to see what workloads will benefit and which ones will not.
Timeframe and Availability
At the presentation, it was given that Zen will be available in volume in 2017. As the AM4 platform will share a socket with Bristol Ridge, users are likely to see Bristol Ridge systems from AMD’s main OEM partners, like Dell and others, enter the market before separate Zen CPUs will hit the market for DIY builders. It’s a matter of principle that almost no consumer focused semiconductor company releases a product for the sale season, and Q1 features such events as CES, which gives a pretty clear indication of when we can expect to get our hands on one.
It’s worth noting that AMD said that as we get closer to launch, further details will come as well as deeper information about the design. It was also mentioned that the marketing strategy is also currently being determined, such that Zen may not actually be the retail product name for the line of processors (we already have Summit Ridge as the platform codename, but that could change for retail as well).
Wrap Up
AMD has gone much further into their core design than I expected this week. When we were told we had a briefing, and there were 200-odd press and analysts in the room, I was expecting to hear some high level puff about the brand and a reiteration of their commitment to the high end. To actually get some slides detailing parts of the microarchitecture, even at a basic cache level, was quite surprising and it somewhat means that AMD might have stolen the show with the news this week.
We’ve got another couple of pieces detailing some of the AMD internal/live benchmark numbers during the presentation, as well as the dual socket server platform, the 32-core Naples server CPU, and what we saw at the event in terms of motherboard design.
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Zingam - Thursday, August 18, 2016 - link
AMD realized finally that there is nothing better in the x86 world than copying Intel.tarqsharq - Thursday, August 18, 2016 - link
The same way Intel copied x86-64 from AMD? Or how AMD put out a superior dual core solution?Copying has gone both ways.
Stuka87 - Thursday, August 18, 2016 - link
Intel did not copy x86-64, they licensed it from AMD.Krysto - Thursday, August 18, 2016 - link
Which by the way is one of the reasons why the argument that "Intel would never allow AMD to be sold to another company" is so STUPID. If they do something like that and somehow retract their own licensing to AMD, let's see how well Intel does in the market without the 64-bit support licensed from AMD......That's why I believe AMD could easily sell itself to Qualcomm or Samsung if it wanted to. Intel may throw a hissy fit, but at the end of the day there's nothing they can do about it. Worst case scenario, whoever buys AMD, has to pay a little more for Intel's IP, but nothing that would break the company.
Kvaern1 - Thursday, August 18, 2016 - link
The licensing agreement is automatically terminated if either part goes through a change of control.Piraal - Thursday, August 18, 2016 - link
If intel wasn't licensed then it would be monopoly for AMD in no time, ever wonder why they licensed intel?Guess what intel licensed x86 to AMD before that for the same reason. It is funny how few people understand why AMD, and Intel before that 'had' to essentially give up something that would destroy their biggest competitor.
Morawka - Thursday, August 18, 2016 - link
IIRC if was part of a settlement between AMD and Intel that lead to the x64 getting licensed. i could be wrong thoSamus - Friday, August 19, 2016 - link
Actually the way I last read the licensing agreement worked is as long as AMD licenses x86, Intel has exclusive use of any AMD innovations in x86. That's how Intel essentially "licensed" x86-64 for free.It's like Mazda licensing a platform to Ford to build, and in return Mazda is allowed to monitor improvements to the platform to use on their own vehicles. This is commonly referred to as a joint venture technology agreement, and although AMD and Intel don't call it that, it's what it appears to be because the fine print of Intel licensing permits them to peak inside architectural improvements.
Note that this has nothing to do with the manufacturing end, unlike my Mazda>Ford analogy which is exclusively manufacturing based.
Anato - Saturday, August 20, 2016 - link
"Actually the way I last read the licensing agreement worked is as long as AMD licenses x86, Intel has exclusive use of any AMD innovations in x86. That's how Intel essentially "licensed" x86-64 for free."I doubt this, as this would mean that terminating AMD would terminate Intel x86-64 license. Think IBM, Samsung, Oracle or Apple buying AMD and stop making x86. Then Intel would not have x86-64 license anymore. So by paying 5-10B$ for AMD you could stop Intel's current 64 license which is >70% (?) of their revenue or use this as ransom.
Samus - Saturday, August 20, 2016 - link
All past-tense licensed innovation is grandfathered in upon a technology agreement termination. Legally. For instance, Mazda and Ford can use each others previous platforms indefinitely.