The AMD Zen and Ryzen 7 Review: A Deep Dive on 1800X, 1700X and 1700
by Ian Cutress on March 2, 2017 9:00 AM ESTThe Core Complex, Caches, and Fabric
Many core designs often start with an initial low-core-count building block that is repeated across a coherent fabric to generate a large number of cores and the large die. In this case, AMD is using a CPU Complex (CCX) as that building block which consists of four cores and the associated caches.
Each core will have direct access to its private L2 cache, and the 8 MB of L3 cache is, despite being split into blocks per core, accessible by every core on the CCX with ‘an average latency’ also L3 hits nearer to the core will have a lower latency due to the low-order address interleave method of address generation.
The L3 cache is actually a victim cache, taking data from L1 and L2 evictions rather than collecting data from prefetch/demand instructions. Victim caches tend to be less effective than inclusive caches, however Zen counters this by having a sufficiency large L2 to compensate. The use of a victim cache means that it does not have to hold L2 data inside, effectively increasing its potential capacity with less data redundancy.
It is worth noting that a single CCX has 8 MB of cache, and as a result the 8-core Zen being displayed by AMD at the current events involves two CPU Complexes. This affords a total of 16 MB of L3 cache, albeit in two distinct parts. This means that the true LLC for the entire chip is actually DRAM, although AMD states that the two CCXes can communicate with each other through the custom fabric which connects both the complexes, the memory controller, the IO, the PCIe lanes etc.
The cache representation shows L1 and L2 being local to each the core, followed by 8MB of L3 split over several cores. AMD states that the L1 and L2 bandwidth is nearly double that of Excavator, with L3 now up to 5x for bandwidth, and that this bandwidth will help drive the improvements made on the prefetch side. AMD also states that there are large queues in play for L1/L2 cache misses.
One interesting story is going to be how AMD’s coherent fabric works. For those that follow mobile phone SoCs, we know fabrics and interconnects such as CCI-400 or the CCN family are optimized to take advantage of core clusters along with the rest of the chip. A number of people have speculated that the fabric used in AMD’s new design is based on HyperTransport, however AMD has confirmed that they are using a superset HyperTransport here for Zen, and that the Infinity fabric design is meant to be high bandwidth, low latency, and be in both Zen and Vega as well as future products. Almost similar to the CPU/GPU roadmaps, the Fabric has its own as well.
Ultimately the new fabric involves a series of control and data passing structures, with the data passing enabling third-party IP in custom designs, a high-performance common bus for large multi-unit (CPU/GPU) structures, and socket to socket communication. The control elements are an extension of power management, enabling parts of the fabric to duty cycle when not in use, security by way of memory management and detection, and test/initialization for activities such as data prefetch.
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deltaFx2 - Wednesday, March 8, 2017 - link
@Meteor2: No. Consumer GPUs have poor throughput for Double precision FP. So you can't push those to the GPU (unless you own those super-expensive Nvidia compute cards). Apparently, many rendering/video editing programs use GPUs for preview but do the final rendering on CPU. Quality, apparently, and might be related to DP FP. I'm not the expert, so if you know otherwise, I'd be happy to be corrected and educated. Also, you could make the same argument about AVX-256.The quoted paragraph is probably the only balanced statement in that entire review. Compare the tone of that review with AT review above.
On an unrelated note, there's the larger question of running games at low res on top-end gpus and comparing frame-rates that far exceed human perception. I know, they have to do something, so why not just do this. The rationale is: " In future a faster GPU in future will create a bottleneck ". If this is true, it should be easy to demonstrate, right? Just dig through a history of Intel desktop CPUs paired with increasingly powerful GPUs and see how it trends. There's not one reviewer that has proven that this is true. It's being taken as gospel. OTOH, plenty of folks seem happy with their Sandy Bridge + Nvidia 1080, so clearly the bottleneck isn't here 5 years after SB. Maybe, just maybe, it's because the differences are imperceptible?
Ryzen clearly has some bottlenecks but the whole gaming thing is a tempest in a tea-cup.
theuglyman0war - Thursday, March 9, 2017 - link
ZBRUSHprobably 90% of all 3d assets that are created from concept ( NOT SCANNED )
Went through Zbrush at some point.
Which means no GPU acceleration at all.
Renderman
Maxwell
Vray
Arnold
still all use CPU rendering As do a mountain of other renderers.
Arnold will be getting an option
But the two popular GPU renderers are Otoy Octane and Redshift...
The have their excellent expensive place. But the majority of rendering out there is still suffered through software rendering. And will always be a valid concern as long as they come FREE built into major DCC applications.
theuglyman0war - Thursday, March 9, 2017 - link
Saw that same GPU trumps CPU render validity concerns...Comment and had a good laugh.
I'll remember to spread that around every time I see Renderman Vray Arnold Maxwell sans GPU rendering going on.
Or the next time a Mercury engine update negates all non Quadro GPU acceleration.
To be fair a lot of creative pros and tech artists seem to disagree with me but...
The only time between pulling vrts in Maya and brushing a surface in Zbrush that I really feel that I am suffering buckets of tears and desire a new CPU ( still on i7-980x ) is when I am cussing out a progress bar that is teasing me with it's slow progress. And that means CORES! encoding... un compressing... Rendering! Otherwise I could probably not notice day to day on a ten year old CPU. ( excluding CPU bound gaming of course... talking bout day to day vrt pulling )
I was just as productive in 2007 as I am today.
MaidoMaido - Saturday, March 4, 2017 - link
Been trying to find a review including practical benchmarks for common video editing / motion graphics applications like After Effects, Resolve, Fusion, Premiere, Element 3D.In a lot of these tasks, the multithreading is not always the best, as a result quad core 6700K often outperforms the more expensive Xeon and 5960X etc
deltaFx2 - Saturday, March 4, 2017 - link
I would recommend this response to the GamersNexus hit piece: https://www.reddit.com/r/Amd/comments/5xgonu/analy...The i5 level performance is a lie.
Notmyusualid - Saturday, March 4, 2017 - link
@ deltaFx2Sorry, not reading a 4k worded response. I'll wait for Anand to finish its Ryzen reviews before I draw any final conclusions.
Meteor2 - Tuesday, March 7, 2017 - link
@deltaFX2 RE: in the 4k word Reddit 'rebuttal', what that person seems to be saying, is that once you've converted your $500 Ryzen 1800X into a 8C/8T chip, _then_ it beats a $240 i5, while still falling short of the $330 i7. Out-of-the-box, it has worse gaming performance than either Intel chip.That's not exactly a ringing endorsement.
The analysis in the Anandtech forums, which concludes that in a certain narrow and low power band a heavily down-clocked 1800X happens to get excellent performance/W, isn't exactly thrilling either.
deltaFx2 - Wednesday, March 8, 2017 - link
@ Meteor2: The anandtech forum thing: Perf/watt matters for servers and laptop. Take a look at the IPC numbers too. His average is that Zen == Broadwell IPC, and ~10% behind Sky/Kaby lake (except for AVX256 workloads). That's not too shabby at all for a $300 part.You completely missed the point of the reddit rebuttal. The GN reviewer drops i5s from plenty of tests citing "methodological reasons", but then says R7==i5 in gaming. The argument is that plenty of games use >4 threads and that puts i5 at a disadvantage.
tankNZ - Sunday, March 5, 2017 - link
yes I agree, it's even better than okay for gaming[img]http://smsh.me/li3a.png[/img]deltaFx2 - Monday, March 6, 2017 - link
You may wish to see this though: https://forums.anandtech.com/threads/ryzen-strictl... Way, way, more detailed than any tech media review site can hope to get. No, it's got nothing to do with gaming. Gaming isn't the story here. AMD's current situation in x86 market share had little to do with gaming efficiency, but perf/watt.I'll quote the author: "850 points in Cinebench 15 at 30W is quite telling. Or not telling, but absolutely massive. Zeppelin can reach absolutely monstrous and unseen levels of efficiency, as long as it operates within its ideal frequency range."