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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m1ngky - Saturday, August 20, 2016 - link
It could be the performance boost is only 5% each generation because there wasn't a need for more due to the monopoly Intel has in the CPU market.Once decent competition from AMD emerges I'm betting we see more of a % boost then.
sonicmerlin - Saturday, August 20, 2016 - link
I seriously doubt it, Intel needs performance boosts to sell new products every year. If they could've then they would've.Byte - Thursday, August 18, 2016 - link
Value of top end K chips actually don't really go down that much. If you want to look for a Haswell devils canon, you still have to pony up around $300, maybe you can find a used one for $250ish, but same can be said for a Skylake. Even a 4770k or 3770k is hard to find for under $250 used. Even a 2770k i sold one not too long ago for $245.Nagorak - Thursday, August 18, 2016 - link
Prices for computer hardware isn't dropping very fast because performance has barely increased. A two year old CPU now is for all intents and purposes is just as good as a brand new one. There may be some marginal situations where the 5% difference in performance matters, but for the most part they perform identically.Compare this to the heyday of the late 90s when a two year old CPU might be half as fast as a new one. It was no surprise that upgrade cycles were shorter and resale values much less.
KPOM - Friday, August 19, 2016 - link
Tell that to all the people on MacRumors complaining that the 13" rMBP still has a Broadwell processor.Icehawk - Sunday, August 21, 2016 - link
While I agree with Nagorak, I have moved from a 2yr cycle to a 4+ cycle on CPU/platforms, I think the Apple folks have a right to gripe about the lack of updates - some of them are a few gens back at this point and prices haven't dropped enough to make up for that IMO.smilingcrow - Thursday, August 18, 2016 - link
Their whole CPU business is based on an Intel license to copy; ignoring the ARM stuff.blublub - Thursday, August 18, 2016 - link
1. Intel's X64 is based on AMD's license.....so what !? (remeber the Itanium disaster?)2. AMD also hold X86 licenses which are used by Inte - both x86 and x64 are cross-licenses
So in the end they both license/copy another -- so what!?
And I am pretty sure after the recent Intel/Nvidia rattle that the next Intel GPUs are being build via AMD's license
smilingcrow - Thursday, August 18, 2016 - link
There’s a massive difference though. AMD only has a license due to IBM insisting on Intel allowing a second manufacturer for its patented x86 CPUs.So AMD has been a parasite living on Intel patents with a degree of symbiosis in the relationship. That makes their various successful phases all the more noteworthy and hopefully Zen leads into another long awaited successful phase.
I think you are jumping to conclusions much to quickly over a mere PR spat with Nvidia.
ddriver - Thursday, August 18, 2016 - link
you are such an obvious intel troll fanboy that its just sad