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 High-Level Zen Overview
AMD is keen to stress that the Zen project had three main goals: core, cache and power. The power aspect of the design is one that was very aggressive – not in the sense of aiming for a mobile-first design, but efficiency at the higher performance levels was key in order to be competitive again. It is worth noting that AMD did not mention ‘die size’ in any of the three main goals, which is usually a requirement as well. Arguably you can make a massive core design to run at high performance and low latency, but it comes at the expense of die size which makes the cost of such a design from a product standpoint less economical (if AMD had to rely on 500mm2 die designs in consumer at 14nm, they would be priced way too high). Nevertheless, power was the main concern rather than pure performance or function, which have been typical AMD targets in the past. The shifting of the goal posts was part of the process to creating Zen.
This slide contains a number of features we will hit on later in this piece, but covers a number of main topics which come under those main three goals of core, cache and power.
For the core, having bigger and wider everything was to be expected, however maintaining a low latency can be difficult. Features such as the micro-op cache help most instruction streams improve in performance and bypass parts of potentially long-cycle repetitive operations, but also the larger dispatch, larger retire, larger schedulers and better branch prediction means that higher throughput can be maintained longer and in the fastest order possible. Add in dual threads and the applicability of keeping the functional units occupied with full queues also improves multi-threaded performance.
For the caches, having a faster prefetch and better algorithms ensures the data is ready when each of the caches when a thread needs it. Aiming for faster caches was AMD’s target, and while they are not disclosing latencies or bandwidth at this time, we are being told that L1/L2 bandwidth is doubled with L3 up to 5x.
For the power, AMD has taken what it learned with Carrizo and moved it forward. This involves more aggressive monitoring of critical paths around the core, and better control of the frequency and power in various regions of the silicon. Zen will have more clock regions (it seems various parts of the back-end and front-end can be gated as needed) with features that help improve power efficiency, such as the micro-op cache, the Stack Engine (dedicated low power address manipulation unit) and Move elimination (low-power method for register adjustment - pointers to registers are adjusted rather than going through the high-power scheduler).
The Big Core Diagram
We saw this diagram last year, showing some of the bigger features AMD wants to promote:
The improved branch predictor allows for 2 branches per Branch Target Buffer (BTB), but in the event of tagged instructions will filter through the micro-op cache. On the other side, the decoder can dispatch 4 instructions per cycle however some of those instructions can be fused into the micro-op queue. Fused instructions still come out of the queue as two micro-ops, but take up less buffer space as a result.
As mentioned earlier, the INT and FP pipes and schedulers are separated, however the INT rename space is 168 registers wide, which feeds into 6x14 scheduling queues. The FP employs as 160 entry register file, and both the FP and INT sections feed into a 192-entry retire queue. The retire queue can operate at 8 instructions per cycle, moving up from 4/cycle in previous AMD microarchitectures.
The load/store units are improved, supporting a 72 out-of-order loads, similar to Skylake. We’ll discuss this a bit later. On the FP side there are four pipes (compared to three in previous designs) which support combined 128-bit FMAC instructions. These can be combined for one 256-bit AVX, but beyond that it has to be scheduled over multiple instructions.
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mapesdhs - Thursday, March 2, 2017 - link
It would be bizarre if they weren't clocked a lot higher, since there'll be a greater thermal limit per core, which is why the 4820K is such a fun CPU (high-TDP socket, 40 PCIe lanes, but only 4 cores so oc'ing isn't really limited by thermals compared to 6-core SB-E/IB-E) that can beat the 5820K in some cases (multi-GPU/compute).Meteor2 - Friday, March 3, 2017 - link
...Silverblue, look at the PDF opening test. What comes top? It's not an AMD chip.Cooe - Sunday, February 28, 2021 - link
Lol, because opening PDF's is where people need/will notice more performance? -_-CPU's have been able to open up PDF's fast enough to be irrelevant since around the turn of the century...
rarson - Thursday, March 2, 2017 - link
"AMD really isn't offering anything much for the mid range or regular desktop user either."So I'd HIGHLY recommend you wait 3 months, or overpay for Intel stuff. Because the lower-core Zen chips will no doubt provide the same performance-per-dollar that the high-end Ryzen chips are offering right now.
rarson - Thursday, March 2, 2017 - link
"their $499 CPU is often beaten by an i3."It's clear that you're looking at raw benchmark numbers and not real-world performance for what the chip is designed. If all you need is i3 performance, then why the hell are you looking at an 8-core processor that runs $329 or more?
Ratman6161 - Friday, March 3, 2017 - link
Its all academic to me. As I posted elsewhere, my i7-2600K is still offering me all the performance I need. So I'm just reading this out of curiosity. I also really, really want to like AMD CPU's because I still have a lot of nostalgia for the good old days of the Athlon 64 - when AMD was actually beating Intel in both performance and price. And sometimes I like to tinker around with the latest toys even if I don't particularly need it. I have a home lab with two VMWare ESXi systems built on FX-8320's because at the time they were the cheapest way to get to 8 threads - running a lot of VM's but with each VM doing light work.I also run an IT department so I'm always keeping tabs on what might be coming down the pike when I get ready to update desktops. But there is a sharp divide between what I buy for myself at home and what I buy for users at work. At work, most of our users actually would do fine with an i3. But I'm also keeping an eye out for what AMD has on offer in this range.
Notmyusualid - Tuesday, March 7, 2017 - link
@ Jimster480Sorry pal, but that is false, or inaccurate information.
ALL BUT the lowest model of CPUs in the 2011v3 platform are 40 PCIE lanes. Again, only the entry-level chip (6800K),has 28 lanes:
http://www.anandtech.com/show/10337/the-intel-broa...
But I do agree with you, that this is competing against the HEDT line.
Peace.
slickr - Thursday, March 2, 2017 - link
I'm sorry, but that sound just like Intel PR. I don't usually call people shills, but your reply seems to be straight out of Intel's PR book! First of all more and more games are taking advantage of more cores, you can easily see this especially with DX12 titles where if you have even 16 cores it will take advantage of.So having 8 cores for $330 to $500 is incredible value! We also see that the Ryzen chips are all competitive compared to the $1100 6900k which is where the comparison should be. Performance on 8 cores.
And as I've found out real world performance on 8 cores compared to 4 cores is like night and day. Have you tried running a demanding game, streaming in through OBS to Twitch, with the browser open to read Twitch chat and check other stuff in the process, while also having musicbee open and playing your songs and a separate program to read Twitch donations and text, etc...
This is where 4 core struggles a lot, while 8 core responsiveness is perfect. I can't use my PC if I decide to reduce a video size to a smaller one with a 4 core. Even 8 cores are fully taken advantage off, but through one core you can always do other stuff like watch movie or surf the internet without it struggling to process.
But even if games are your holy grail and what you base your opinion on, then Ryzen does really well. Its equal or slightly slower than the much much more optimized Intel processors. But you have to keep in mind a lot of the game code is optimized solely for Intel. That is what most gamers use, in fact over 80% is Intel based gamers, but developers will optimize for AMD now that they have a competitor on their hands.
We see this all the time, with game developers optimizing for RX 400 series a lot, even though Nvidia has the large majority of share in the market. So I expect to see anywhere from 10% to 25% more performance in games and programs that are also optimized for AMD hardware.
lmcd - Thursday, March 2, 2017 - link
How can you call someone a shill and post this without any self-awareness? Your real-world task is GPU-constrained anyway, since you should be using a GPU capable of both video encode and rendering simultaneously. If not, you can consider excellent features like Intel's Quick Sync, which works even with a primary GPU in use these days.Meteor2 - Friday, March 3, 2017 - link
Game code is optimised for x86.