AMD Zen 2 Microarchitecture Analysis: Ryzen 3000 and EPYC Rome
by Dr. Ian Cutress on June 10, 2019 7:22 PM EST- Posted in
- CPUs
- AMD
- Ryzen
- EPYC
- Infinity Fabric
- PCIe 4.0
- Zen 2
- Rome
- Ryzen 3000
- Ryzen 3rd Gen
Performance Claims of Zen 2
At Computex, AMD announced that it had designed Zen 2 to offer a direct +15% raw performance gain over its Zen+ platform when comparing two processors at the same frequency. At the same time, AMD also claims that at the same power, Zen 2 will offer greater than a >1.25x performance gain at the same power, or up to half power at the same performance. Combining this together, for select benchmarks, AMD is claiming a +75% performance per watt gain over its previous generation product, and a +45% performance per watt gain over its competition.
These are numbers we can’t verify at this point, as we do not have the products in hand, and when we do the embargo for benchmarking results will lift on July 7th. AMD did spend a good amount of time going through the new changes in the microarchitecture for Zen 2, as well as platform level changes, in order to show how the product has improved over the previous generation.
It should also be noted that at multiple times during AMD’s recent Tech Day, the company stated that they are not interested in going back-and-forth with its primary competition on incremental updates to try and beat one another, which might result in holding technology back. AMD is committed, according to its executives, to pushing the envelope of performance as much as it can every generation, regardless of the competition. Both CEO Dr. Lisa Su, and CTO Mark Papermaster, have said that they expected the timeline of the launch of their Zen 2 portfolio to intersect with a very competitive Intel 10nm product line. Despite this not being the case, the AMD executives stated they are still pushing ahead with their roadmap as planned.
| AMD 'Matisse' Ryzen 3000 Series CPUs | |||||||||||
| AnandTech | Cores Threads |
Base Freq |
Boost Freq |
L2 Cache |
L3 Cache |
PCIe 4.0 |
DDR4 | TDP | Price (SEP) |
||
| Ryzen 9 | 3950X | 16C | 32T | 3.5 | 4.7 | 8 MB | 64 MB | 16+4+4 | 3200 | 105W | $749 |
| Ryzen 9 | 3900X | 12C | 24T | 3.8 | 4.6 | 6 MB | 64 MB | 16+4+4 | 3200 | 105W | $499 |
| Ryzen 7 | 3800X | 8C | 16T | 3.9 | 4.5 | 4 MB | 32 MB | 16+4+4 | 3200 | 105W | $399 |
| Ryzen 7 | 3700X | 8C | 16T | 3.6 | 4.4 | 4 MB | 32 MB | 16+4+4 | 3200 | 65W | $329 |
| Ryzen 5 | 3600X | 6C | 12T | 3.8 | 4.4 | 3 MB | 32 MB | 16+4+4 | 3200 | 95W | $249 |
| Ryzen 5 | 3600 | 6C | 12T | 3.6 | 4.2 | 3 MB | 32 MB | 16+4+4 | 3200 | 65W | $199 |
AMD’s benchmark of choice, when showcasing the performance of its upcoming Matisse processors is Cinebench. Cinebench a floating point benchmark which the company has historically done very well on, and tends to probe the CPU FP performance as well as cache performance, although it ends up often not involving much of the memory subsystem.
Back at CES 2019 in January, AMD showed an un-named 8-core Zen 2 processor against Intel’s high-end 8-core processor, the i9-9900K, on Cinebench R15, where the systems scored about the same result, but with the AMD full system consuming around 1/3 or more less power. For Computex in May, AMD disclosed a lot of the eight and twelve-core details, along with how these chips compare in single and multi-threaded Cinebench R20 results.
AMD is stating that its new processors, when comparing across core counts, offer better single thread performance, better multi-thread performance, at a lower power and a much lower price point when it comes to CPU benchmarks.
When it comes to gaming, AMD is rather bullish on this front. At 1080p, comparing the Ryzen 7 2700X to the Ryzen 7 3800X, AMD is expecting anywhere from a +11% to a +34% increase in frame rates generation to generation.
When it comes to comparing gaming between AMD and Intel processors, AMD stuck to 1080p testing of popular titles, again comparing similar processors for core counts and pricing. In pretty much every comparison, it was a back and forth between the AMD product and the Intel product – AMD would win some, loses some, or draws in others. Here’s the $250 comparison as an example:
Performance in gaming in this case was designed to showcase the frequency and IPC improvements, rather than any benefits from PCIe 4.0. On the frequency side, AMD stated that despite the 7nm die shrink and higher resistivity of the pathways, they were able to extract a higher frequency out of the 7nm TSMC process compared to 14nm and 12nm from Global Foundries.
AMD also made commentary about the new L3 cache design, as it moves from 2 MB/core to 4 MB/core. Doubling the L3 cache, according to AMD, affords an additional +11% to +21% increase in performance at 1080p for gaming with a discrete GPU.
There are some new instructions on Zen 2 that would be able to assist in verifying these numbers.
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nonoverclock - Wednesday, June 12, 2019 - link
It's related to platform power management.wurizen - Wednesday, June 12, 2019 - link
"Raw Memory Latency" graph shows 69ns for for 3200 and 3600 Mhz RAM. This "69ns" is irrelevant, right? Isn't the "high latency" associated with Ryzen and IF due to "Cross-CCX-Memory-Latency? This is suppose to be ~110ns at 3200 Mhz RAM as tested by PCPER/etc.... This in my experiences causes "micro-stuttering" in games like BO3/BF4/etc.... And, a "Ryzen-micro-stutter/pause" is different than a micro-stutter/pause associated with Intel. With Intel the micro-stutter/pause happens in BFV, for example, but they happen once or twice per match. With Ryzen, not only is the quality/feeling of the "micro-stutter/pause" different (seems worst), but it is constant throughout the match. One gets a feeling that it is not server-side, GPU side, nor WIndows 10 side. But, CPU-side issue... Infinity Fabric side. So, now Inifinity Fabric 2 is out. Is it 2.0 as in better? No more high latency? Is that 69ns Cross-CCX-memory latency? Why is AMD and Tech sites like Anand so... like... not talking about this?igavus - Wednesday, June 12, 2019 - link
You are misattributing things here. Your stutter is most def. not caused by memory access latency variations. For it to be visible on even an 144Hz monitor with the game running at the native rate, the differences would have to be obscenely high. That's just unrealistic.Not that it helps to determine what is causing your issues, but that's not it.
wurizen - Wednesday, June 12, 2019 - link
What?wurizen - Wednesday, June 12, 2019 - link
Maybe, you guys don't know what Cross-CCX-Memory-Latyency is... my main goal of commenting was what that SLIDE showing "Raw Memory Latency" refers to? Is it Inter-core-memory or Intra-core-memory (intra-core is the same as cross-ccx-memory)...inter-core memory is data being shuffled within the cores in a CCX module. Ryzen and Ryzen + had two CCX modules with 4 cores each, totaling 8 cores for the 2700x, as an example. If, the memory/data is traveling in the same CCX, the latency is fine and is even faster than Intel. This was true with Ryzen and Ryzen +.
The issue is when data and memory is being shuffled between the CCX modules, and when traversing the so called "Infinity Fabric." Intel uses a Ring Bus and doesn't have an equivalent measurement and data. Intel does have MESH with the x299 which is similar-ish to AMD's CCX and IF. But, Intel Mesh latency is lower (I think. But havent dug around since I dont care about it since I cant afford it)....
So... that is what Cross-CCX-memory-latency is... and that SLIDE shown on this article... WTF does that refer to? 69ns is similar to Intel Ring Bus memory latency, which have shown to be fast enough and is the standard in regards to latency that won't cause issues...
So... as PCPER tested, Ryzen Infinity Fanri 1.0 has a cross-ccx-latnecy to be around 110ns... and I stand my ground (its not bios/reinstallwindows/or windows scheduler/or user-error/or imperceptible/or a misunderstanding / or a mis-atribution (I think)) that it was the reason why I suffered "micro-pauses/stutters in some games. I had two systems at the time (3700k and R7-1700x) and so I was able to diagnose/observe/interpret what was happening....
Also.. I would like to add that the "Ryzen Micro-stutter-Pause" FEELS/LOOKS/BEHAVES different... weird, right?
deltaFx2 - Thursday, June 13, 2019 - link
You might "stand your ground" but that doesn't make it true. First of all, it's pretty clear you don't understand what you're talking about. Intel's Mesh is NOTHING like AMD's CCX. Intel Mesh is an alternative interconnect to ring bus; mesh scales better to many cores relative to ring. In theory mesh should be faster but for whatever reason intel's memory latency on skylake X parts are quite bad relative to skylake client (i.e. no bueno for gaming). I recall 70ns-ish for Skylake X vs 60ns for the Skylake client.Cross CCX memory latency should not matter unless you have shared memory across threads that span CCXs. Games don't need that many threads: 8 is overkill in many cases and each CCX can comfortably handle 8. Unless you pinned threads to cores and ran an experiment that conclusively showed that the issue was inter-ccx latency (I doubt it), your standing ground doesn't mean much. One could just as well argue that the microstutter was due to driver issues or other software/bios issues. Zen has been around for quite some time and if this was a widespread problem, we'd know.
wurizen - Friday, June 14, 2019 - link
Well, I did mention "similar-ish" of Mesh to Infinity Fabric. It's meshy. And, i guess, you get "comraderie" points for calling me out as "pretty clear you don't understand what you're talking about." That hurts, man! :("In theory... Mesh should be faster..." nice way to switch subjects, bruh. yeh, i can throw some at ya, bruh! what?
Cross-CCX-High-Memory-Latency DOES MATTER!
You know why? Because a game shuffles data randomly. It doesn't know that traversing said Data from Core 0 (residing in CCX 1) to Core 3 (in CCX 2) via Infinity Fabric means that there is a latency penalty.
Bruh
deltaFx2 - Friday, June 14, 2019 - link
Actually, no, you're wrong about the mesh. Intel has a logically unified L3 cache; i.e. any core can access any slice of the L3, or even one core can use the entire L3 for itself. AMD has a logically distributed L3 cache which means only the cores from the CCX can access its cache. You simply cannot have core 3 (CCX 0) fetch a line into CCX1's cache. The tradeoff is that the distributed L3 is much faster than the logically unified one but the logically unified one obviously offers better hit rates and does not suffer from sharing issues."Cross-CCX-High-Memory-Latency DOES MATTER!" Yes it does, no question about that. It matters when you have lock contention or shared memory that spans CCXs. In order to span CCXs, you should be using more than 8 threads (4 cores to a CCX, 2 threads per core). I don't think games are _that_ multithreaded. This article mentions a Windows 10 patch to ensure that threads get assigned to the same CCX before going to the adjacent one. It can be a problem for compute-intensive applications (y'know, real work), but games? I doubt it, and you should be able to fix it easily by pinning threads to cores in the same CCX.
deltaFx2 - Friday, June 14, 2019 - link
"shared memory that spans CCXs." -> shared DIRTY memory. i.e. core 8 writes data, core 0 wants to read. All other kinds of sharing are a non-issue. Each CCX gets a local copy of the data.wurizen - Friday, June 14, 2019 - link
Why do you keep on blabbing on about this? Are you trying to fix some sort of muscle?