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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MonkeyPaw - Thursday, August 18, 2016 - link
Heck, people are forgetting some significant firsts for AMD--the first to bring the IMC and hypertransport to x86. Both were big for the server world, too.smilingcrow - Friday, August 19, 2016 - link
Innovation is good and AMD have had many moments in the sun but let's not forget that Core 2 duo lacked an IMC and still trounced the AMD competition.Good products matter more than innovation and the trick is to turn innovation into good products.
The_Countess - Saturday, August 20, 2016 - link
and lets not forget the first with a on-die memory controller for a x86 CPU. a huge improvement on both the desktop and the server space. it basically is what made more then 2 socket motherboards viable at all.Kevin G - Saturday, August 20, 2016 - link
Intel had a 386 chip with an integrated memory controller back in 90's so AMD wasn't the first to do it even in the x86 segment.looncraz - Saturday, August 20, 2016 - link
Pretty sure they did not, they had memory management techs built-in, but not memory controllers. The 286 had memory management capabilities as well, and so did all of AMD's comparable CPUs, naturally.The_Countess - Sunday, August 21, 2016 - link
that would be the first time i heard about that so: source?Kevin G - Sunday, August 21, 2016 - link
80386EX for the embedded market. Came out in 1994. By this time, it was two generations behind the Pentium so it generated very little fan fair.http://news.softpedia.com/news/Intel-Wants-The-Emb...
Here is a book that includes some details about the 80386EX, though you'll have to do a bit of digging in it:
http://userpages.umbc.edu/~squire/intel_book.pdf
Gigaplex - Thursday, August 18, 2016 - link
"AMD was first with CPU + GPU = APU."Llano came out June 2011. Intel had Westmere (January 2010) and Sandy Bridge (January 2011) before Llano. Even if you discount Westmere since they were separate dies on the same package, Sandy Bridge still got there before Llano.
Mahigan - Thursday, August 18, 2016 - link
https://www.sec.gov/Archives/edgar/data/2488/00011...Intel and AMD have a cross-licensing agreement which covers patents and technologies from both firms allowing both firms to use a rather generous amount of patents from their competitor.
Nobody copied nobody. The two companies are quite intertwined tbh.
Mahigan - Thursday, August 18, 2016 - link
"Advanced Micro Devices has clarified terms of the cross-license agreement with Intel Corp. on Thursday. As it appears, if either AMD or Intel change their control (i.e., gets acquired), the cross-license agreement between the two companies is automatically terminated for both parties.AMD and Intel have a cross-licensing agreement, which guarantees that the companies will not pursue litigation for any potential patent infringements. The agreement covers entire patent portfolio for both companies, which includes general-purpose processors, graphics adapters and other intellectual property. For example, AMD can design and sell microprocessors compatible with Intel’s x86 instruction set architecture and featuring a variety of extensions, whereas Intel can develop and ship central processing units that utilize IP and extensions initially created by AMD . The cross-licensing agreement has a number of terms and limitations. For example, the chip designers are not allowed to build processors that are compatible with competitor’s infrastructure (e.g., sockets, mainboards, etc.). Besides, if AMD and Intel change their ownership , the agreement terminated."
http://www.kitguru.net/components/cpu/anton-shilov...