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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wumpus - Thursday, August 18, 2016 - link
I want this chip (or a semi-low priced i7 with the graphics removed and 4 more cores in its place) with HBM[2-3] memory (and presumably all the DRAM that fits. Hopefully in 5 years that doesn't imply a transition die) and xpoint as "main memory - SSD buffer/cache/'SSD dram'"So yes, five years at least.
ikjadoon - Thursday, August 18, 2016 - link
No, I think it theoretically is very relevant. If those QD1 numbers are to be believed, we should see noticeable performance increases in day-to-day usage, right?Exactly: it's a fantasy at the price points that are palatable to *consumers*, hehe. Prosumers are also buying $1000+ GPUs, hehe...not the same market.
Right....and that transition is still many years away.
So, what I meant....IDF16 is not very interesting for consumers. AMD timed this presentation quite well.
smilingcrow - Thursday, August 18, 2016 - link
I am not sure that the QD1 numbers will really make a noticeable difference for general consumer usage patterns. Have to wait for real world benchmarks.azazel1024 - Thursday, August 18, 2016 - link
I was very meh about Zen, but now I am actually kind of anticipating it. Even with some of the early engineering sample leaks and rumors that it will be improved IPC, possibly even right up on Skylake, but with much lower clocks. meaning it'll still be lower single threaded performance doesn't bother me too much. BD and it's kin are generally extremely poor single thread compared to Intel's latest Core processors. If Zen comes a fair amount closer...but does it while having 8 cores and 16 threads...that to me says it might actually have a good shot at being in between Skylake/Broadwell and Broadwell-E. If it can do that at a lower price point and being in spitting distance of single thread performance AND manage vaguely reasonable power consumption figures, you could count me as a buyer (if AM4 socketed boards have decent bus support).Give me a Zen with 80-90% of the single thread of Broadwell-E and 80-90% of the mutlthreaded performance of an Octocore Broadwell-E at the price of an entry level Broadwell-E Hexacore, or even a little less ($250-350) and you could count me as a buyer, so long as it isn't some 150TDP monster.
jjj - Thursday, August 18, 2016 - link
Intel rates Broadwell-E at 140W while Zen 8 cores is supposed to be 95W.We'll see about base clocks and Turbo clocks but power might end up being very interesting.
Ofc die size will be interesting too and they should have 4 cores 65W with no GPU.
smilingcrow - Friday, August 19, 2016 - link
Keep in mind that the TDP for the E range tends to be the same for the whole range so in practice the chips below the top of the stack may in reality be capable of using a lower TDP.patel21 - Thursday, August 18, 2016 - link
For me, a performance comparable to i3 skylake, with power requirements at max over 20% of i3, with a good gpu integrated and at around 70% of i3's price. And My boat will sail AMD....Ho yaanandnandnand - Thursday, August 18, 2016 - link
Weren't "8-core" Bulldozer/Excavator chips sold around $200-250? Maybe it's not so crazy to say that AMD will sell Zen real 8-cores in that price range.80% single threaded of Broadwell-E, 80% multithreaded performance, $225. How does that sound?
Gigaplex - Thursday, August 18, 2016 - link
If Zen is much faster than Bulldozer, expect it to cost quite a bit more. Bulldozer sold for peanuts because nobody wanted it.StrangerGuy - Thursday, August 18, 2016 - link
Didn't you already know AMD fanboys have the right to be self-entitled cheapskates?"I want AMD to be competitive but without the competitive price tag along with it because evil Intel/NV."