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.
Facebook
Twitter
RSS
574 Comments
View All Comments
BurntMyBacon - Friday, March 3, 2017 - link
@ShieTar: "Well, the point of low-resolution testing is, that at normal resolutions you will always be GPU-restricted."If this statement is accepted as true, then by deduction, for people playing at normal (or high) resolutions, gaming is not a differentiator and therefore unimportant to the CPU selection process. If gaming is your only criteria for CPU selection, then that means you can get the cheapest CPU possible until you are not GPU restricted.
@ShieTar: "The most interesting question will be how Ryzen performs on those few modern games which manage to be CPU-restricted even in relevant resolutions, e.g. Battlefield 1 Multiplayer."
I agree here fully. Show CPU heavy titles to tease out the difference between CPUs. Artificially low resolutions are academic at best. That said, according to Steam Surveys, just over half of their respondents are playing at resolutions less than 1080P. Over a third are playing at 1366x768 or less. Though, I suspect the overlap between people playing at these resolutions and people using high end processors is pretty small.
Average frame rate is fairly uninteresting in most games for high end CPUs, due to being GPU bound or using unrealistic settings. Some, more interesting, metrics are min frame rate, frame time distribution (or simply graph it), frame time consistency, and similar. These metrics do more to show how different CPUs will change the experience for the player in a configuration the player is more likely to use.
Lord-Bryan - Thursday, March 2, 2017 - link
Who buys a 500 dollar cpu to play games at 720p res. All that talk is just BS.JMB1897 - Friday, March 3, 2017 - link
That test is not done for real world testing reasons. At that low resolution, you're not GPU bound, you're CPU bound. That's why the test exists.Now advance a few years into the future when you still have your $500 Ryzen 7 CPU and a brand new GPU - you may suddenly become CPU bound even at QHD or 4k, whereas a 7700k might not quite be CPU bound just yet.
MAC001010 - Saturday, March 4, 2017 - link
Or a few years in the future (when you get your new GPU) you find that games have become more demanding but better multi-threaded, in which case your Ryzen 7 CPU works fine and the 7700k has become a bottleneck despite its high single-threaded performance.This illustrates the inherent difficulty of comparing high freq. CPUs to high core count CPUs in regards to future potential performance.
cmdrdredd - Saturday, March 4, 2017 - link
"Or a few years in the future (when you get your new GPU) you find that games have become more demanding but better multi-threaded, in which case your Ryzen 7 CPU works fine and the 7700k has become a bottleneck despite its high single-threaded performance."Maybe, the overclocking scenario is also important. Most gamers will overclock to get a bit of a boost. I have yet to replace my 4.5Ghz 3570k even though new CPUs offer more raw performance, the need hasn't been there yet.
One other interesting thing is how Microsoft's PlayReady 3.0 will be supported for 4k HDR video content protection. So far I know Kaby Lake supports it, but haven't heard about any of AMD's offerings unless I missed it somewhere.
Cooe - Sunday, February 28, 2021 - link
Lol, except here in reality the EXACT OPPOSITE thing happened. A 6-core/12-thread Ryzen 5 1600 still holds up GREAT in modern titles/game engines thanks to the massive advantage in extra CPU threads. A 4c/4t i5-7600K otoh? Nowadays it performs absolutely freaking TERRIBLY!!!basha - Thursday, March 2, 2017 - link
all the reviews i read are using NVidia 1080 gfx card. my understanding is AMD graphics has better implementation of DX12 with ability to use multiple cores. I would like to see benchmarks with something like RX480 crosfire with 1700x. this would be in the similar budget as i7 7700 + GTX 1080.Notmyusualid - Friday, March 3, 2017 - link
http://www.gamersnexus.net/hwreviews/2822-amd-ryze...cmdrdredd - Saturday, March 4, 2017 - link
Overclocking will be interesting. I don't use my PC for much besides gaming and lately it hasn't been a lot of that either due to lack of compelling titles. However, I would still be interested in seeing what it can offer here too for whenever I finally break down and decide I need to replace my 3570k @ 4.5Ghz.Midwayman - Thursday, March 2, 2017 - link
Here's hoping the 1600x hits the same gaming benches as the 1800x when OC'd. $500 for the 1800x is fine, Its just not the best value for gaming. Just like the i5's having been better value gaming systems in the past.