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Naples, Rome, Milan, Zen 4: An Interview with AMD CTO, Mark Papermaster
The goal of AMD's event in the middle of the fourth quarter of the year was to put into perspective two elements of AMD's strategy: firstly, its commitment to delivering a 7nm Vega based product by the end of the year, as the company promised in early 2018, but also to position its 7nm capabilities as some of the best by disclosing the layout of its next generation enterprise processor set to hit shelves in 2019. [...] We sat down with AMD's CTO, Mark Papermaster, to see if we could squeeze some of the finer details about both AMD's strategy and the finer points of some of the products from the morning sessions.
[...] Ian Cutress: Forrest explained on the stage that the datacenter of today is very different to the datacenter ten years ago (or even 3-5 years ago). What decisions are you making today to predict the datacenter of the future?
Mark Papermaster: We believe we will be positioned very well – it all ties back to my opening comments on Moore's Law. We all accept that the traditional Moore's Law is slowing down, and that while process does still matter you have to be agile about how you put the pieces together, otherwise you cannot win. We leveraged ourselves to have scalability in our first EPYC launch. We leveraged our ability in our chiplet approach here to combine really small 7nm CPU dies with tried and proven 14nm for the IO die. That modularity only grows in importance going forward. We've stated our case as to where we believe it is necessary to keep pace on a traditional Moore's Law growth despite the slowing of the process gains per node and the length of time between major semiconductor nodes. I think you'll see others adopt what we've done with the chiplet approach, and I can tell you we are committed.
[...] IC: Where does Rome sit with CCIX support?
MP: We didn't announce specifically those attributes beyond PCIe 4.0 today, but I can say we are a member of CCIX as we are with Gen Z. Any further detail there you will have to wait until launch. Any specific details about the speeds, feeds, protocols, are coming in 2019.
IC: There have been suggestions that because AMD is saying that Rome is coming in 2019 then that means Q4 2019.
MP: We're not trying to imply any specific quarter or time frame in 2019. If we look at today's event, it was timed it to launch our MI60 GPU in 7nm which is imminent. We wanted to really share with the industry how we've embraced 7nm, and preview what's coming out very soon with MI60, and really share our approach on CPU on Zen 2 and Rome. We're not implying any particular time in 2019, but we'll be forthcoming with that. Even though the GPU is PCIe 3.0 backwards compatible, it helps for a PCIe 4.0 GPU to have a PCIe 4.0 CPU to connect to!
[...] IC: One of the key aspects in AMD's portfolio is the Infinity Fabric, and with Rome you have stated that AMD is now on its second generation IF. Do you see an end in its ability to scale down in process node but also scale out to more chiplets and different IP?
MP: I don't see an end because the IF is made of both of Scalable Data Fabric and a Scalable Control Fabric. The SCF is the key to giving the modularity and that's an architectural product. With our SDF we are very confident on the protocols we developed. The SCF protocols are based on the rich history we have with HyperTransport and we are committed in it generationally to improve bandwidth and latency every generation. IF is important when it applies to on chip connectivity, but it can go chip to chip like we did with EPYC, and also with Vega Radeon Instinct in connecting GPU to GPU. For the chip to chip IF, you are also dependent on the package technology. We see tremendous improvements in package technology over the next five years.
See also: AMD Shows Off "Rome" Data Center CPU, Signs Amazon as Cloud Chip Customer
Previously: AMD Previews Zen 2 Epyc CPUs with up to 64 Cores, New "Chiplet" Design
(Score: 2) by RamiK on Wednesday November 14 2018, @02:00PM (2 children)
Yup.
Itanium wasn't out-of-order so it shouldn't be affected by speculative execution vulnerabilities. MIPS is in-order too. I'm sure if you'd look hard enough you could find hardware equivalent to 10yr/old Intel CPUs that can work as a simple desktop or even a server. But nothing in production since most of those companies switched to ASIC cryptomining a few years ago.
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(Score: 2) by bzipitidoo on Thursday November 15 2018, @05:48AM (1 child)
Out of order execution alone isn't speculative execution. Speculative execution is executing both continuations after a branch, then discarding whichever one was not taken. If no branch is involved. everything will eventually be executed in whatever order the CPU logic determines is best, but it will all be executed, there's no speculation.
The root of the problem is that the checks for permission to access any memory that might be involved are performed after speculating, when it should be performed before doing any speculation. Obviously it's a big performance boost to delay such checks. Evidently, the designers thought they could get away with not ever having to make those checks at all if the code is not ultimately on the execution path. It's kind of like just letting someone log in and have a few seconds use of an account, before checking the password, then kicking them out if the password is wrong.
(Score: 2) by RamiK on Thursday November 15 2018, @05:34PM
That's irrelevant since the cache is unaffected by the mispredicts if you're waiting for the previous instruction to complete between dispatch and issue as you do in a in-order machine. That is, regardless if you're exploiting out-of-order execution (Meltdown) or speculative execution (Spectre), you still the machine to be an out-of-order.
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