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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Reww - Friday, August 19, 2016 - link
Neither AMD or Intel invented the microprocessor, so they're both copying from someone. Now that we cleared that up, everyone can stfu about copying.BillBear - Saturday, August 20, 2016 - link
I will be thrilled to see AMD be competitive on more than price. If AMD is also competitive on performance it's a huge win for consumers.SlyNine - Saturday, August 20, 2016 - link
I almost expected Anand himself to come back and review this one.FireSnake - Monday, August 22, 2016 - link
Where did he go, anyway? Does anybody know?patel21 - Tuesday, August 23, 2016 - link
Some commenters say he is working for Apple nowJohan Steyn - Monday, August 22, 2016 - link
So many people here are defending Intel. Yes AMD has floundered. They have been poor competition to Intel. They are are struggling and maybe even a dying company. It will be a miracle if this chip will be successful, yet I do believe in miracles. I just hate having an Intel CPU in my notebook.Why is this so? Intel is the bully in town and they bullied AMD to death (almost). I have been in this business at that time. Companies were basically forced not to sell AMD. Intel was found guilty of it and got a slap on the wrist for it. $1B is nothing for them. For this I would welcome the day Intel dies a slow (make it rather quicker) and painful death. But this will probably not happen.
People say it it is just business, well it is in my books not ethical business even though it might be legal. It was even found to be illegal, yet with it they killed their opponent. These days many contractors do the same. When they build a building, the law requires a certain amount of parking space (in our country). If they do not do this, they are fined. Parking brings in little compensation and therefore they rather pay the fines, even if the fine are relatively high. This is what Intel did. They new they did wrong, but also new that the repercussions will be minimal. It was worth it for them to kill the competition by breaking the law and be fined. Intel might be your hero, not mine.
This is sickening. Intel makes me sick. I really hope AMD has some success with Zen, even though I think Intel will find another devious way to curb AMD's success. I even hope ARM will eventually dethrone Intel.
Outlander_04 - Monday, August 22, 2016 - link
AMD have surpassed intel in the past . Some of us are old enough to remember 1800 Mhz Athlon 64's smashing intel P4's running at 3000+ MHz .We also remember intels response that saw them bribe oems to continue using their crappy processors by sending back bags of cash to people still buying from them .
We also remember the fines and penalties intel eventually paid for their price fixing. Price fixing that cost their fanboys because it kept the prricee of theeir processors aartificiaally high eveen though they were junk .
A strong AMD is in everyones benefit . We will get more powerful processors and we will get them at a reasonable price . Lets hope ZEN is even better than it seems
sharath.naik - Tuesday, August 23, 2016 - link
The Problem with AMD is that being a technical company, they should have realized lying repeatedly in the name of marketing about the performance of their products, is akin to crying wolf. For now, it does not matter if they actually have a good product or not. The General assumption is that this is going to be another falsehood, and likely their chip can match intel at 3 ghz only when one core is running (That too when turbo is disabled on intel). And will fall far behind both in single and multithread when there is no trubo restriction on the intel chipslyronit - Tuesday, August 23, 2016 - link
I agree with you, but if there's something that can kill Intel at this point, it would be ARM based chips, not AMD.atomsymbol - Monday, August 22, 2016 - link
Bulldozer and Piledriver have a write-through L1D cache. Pentium4 has a write-through L1D cache. Zen has a write-back L1D cache. Skylake has a write-back L1D cache.