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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FMinus - Thursday, August 18, 2016 - link
He's right tho. AMD was a licensee of Intel to produce bulk Intel products, because intel couldn't keep up with the demand. Then AMD reverse engineered Intels products and brought their own line out and Intel didn't like that, thus they broke the agreement, which in the end didn't help much since AMD had already all they needed.That being said, what AMD did anyone would, so it's just business as per usual. Then they actually stepped up and made great own CPUs to combat intel and made a great dual core and AMD64. AMD did a lot for computing, but the early days were pretty much a contractor and pirate.
I wish them all the best with Zen and future, and I hope they get Vega right, by that I mean don't fucking gimp the chip by power delivery, cause you can't get that under control, everyone knows nvidia is ahead in that game, just give a great performing GPU on the market and let it eat 250W if need be.
Nagorak - Thursday, August 18, 2016 - link
Yeah, they matched Intel on the CPU front, and Intel responded by abusing their stronger market position to limit AMD's gains. I'll be happy to get an AMD processor back in my machine just based on principle.Klimax - Saturday, August 20, 2016 - link
Correction: IBM forced Intel to license number of CPU manufactures. (At least two suppliers, similar to rule sued by militaries) And there was lawsuit or two. Fun stuff.looncraz - Thursday, August 18, 2016 - link
Maybe you are too young to remember, but AMD has historically been a primary driver in processor innovation.They created the first native multi-core dies, broke the Ghz barrier, first to debut dynamic clock speeds, invented the seamless x64 transition and AMD64 instruction set, created CMT, created HSA, created the APU, and so much more. And I'm only focusing on CPUs, here.
Intel uses a great deal of AMD tech, and vice-versa.
smilingcrow - Thursday, August 18, 2016 - link
I used to buy AMD exclusively but they have been second rate for 10 years now.I don't buy innovations I buy products and AMD have really struggled for a decade to offer decent products unless your main criteria is value.
Value is fine but for mobile products where power consumption is very important and for workstations where performance is king AMD have had nothing to compete.
I'm very glad that Zen is looking as if it will compete at the higher end although I think they will find it harder to compete with Core M.
Just because I don't view AMD through ten year old rose tinted glasses doesn't mean I don't want them to succeed.
I have been feeling confident for Zen as an 8c/16t chips for ages but it's how it does as a 4c/8t chip that may well be more important in the consumer space unless the 8c/16c chip is unusually cheap for its performance level which it could even be.
Some people here can't tell the difference between someone who is critical of AMD's failings and an Intel fanboy. Intel have their issues but they have delivered decent chips in the decade that AMD fell into disarray. I'm not loyal to incompetent companies.
Nagorak - Thursday, August 18, 2016 - link
It's been hard for anyone to stick with AMD for the last decade. Phenom and Phenom II came up short, and then Bulldozer turned out to be a total disaster. In retrospect AMD should have tossed Bulldozer in the trash and started work on a new processor design immediately. Trying to iterate on that failed design is what almost killed AMD.Gigaplex - Thursday, August 18, 2016 - link
"Created the APU".That's not entirely accurate. Intel was actually first to market with their "APU" type CPUs, even though AMD announced theirs first.
KPOM - Friday, August 19, 2016 - link
These days ARM (soon SoftBank) is the company that keeps Intel management up at night. Intel missed the boat on mobile.Kevin G - Saturday, August 20, 2016 - link
The first dual core chip was POWER4 from IBM.Dynamic clock speeds existed in mobile (think ARM/MIPS) designs back in the 90's.
Seamless x86 transition could be credited to Transmeta for thei VLIW based Crusoe line of chips running x86 code. Runner up could be the FX32! emulator that ran unmodifed x86 Windows binaries in Alpha based hardware back in the 90's.
CMT was done beforehand in Sun's Niagra chip. There designs even before that did unit sharing for CMT.
Elements of HSA came from 3Dlabs and their cards supporting a unified virtual address space.
Integrating a CPU and GPU was first done by Intel though they never shipped it due to relaying on a flawed RDRAM to SDRAM buffer chip:
http://m.theregister.co.uk/2007/02/06/forgotten_te...
Thus the only innovation on your list is the 1 Ghz clock rate for a CPU, which isn't that innovative.
Klimax - Saturday, August 20, 2016 - link
Sorry, wrong. Multicores weren't AMD''s invention, dynamic clock speeds were parallel execution, x64 transition si AMD win only thanks to Microsoft who killed Intel's own development, CMT is not AMD¨s invention (and I would say it is nothing to be proud of), HSA is just label for preexisting technologies, APU was done before AMD's own (in fact, Intel had APU-like chip in late 80s),. AMD didn't invent much as most of technologies were bought in previous acquisitions like HyperTransport (See DEC Alpha)Sorry, to tell you, but what you posit is pure fantasy. AMD inveted very few things and fewer of them were of much importance or use.