Translating to IPC: All This for 3%?

Contrary to popular belief, increasing IPC is difficult. Attempt to ensure that each execution port is fed every cycle requires having wide decoders, large out-of-order queues, fast caches, and the right execution port configuration. It might sound easy to pile it all on, however both physics and economics get in the way: the chip still has to be thermally efficient and it has to make money for the company. Every generational design update will go for what is called the ‘low-hanging fruit’: the identified changes that give the most gain for the smallest effort. Usually reducing cache latency is not always the easiest task, and for non-semiconductor engineers (myself included), it sounds like a lot of work for a small gain.

For our IPC testing, we use the following rules. Each CPU is allocated four cores, without extra threading, and power modes are disabled such that the cores run at a specific frequency only. The DRAM is set to what the processor supports, so in the case of the new CPUs, that is DDR4-2933, and the previous generation at DDR4-2666. I have recently seen threads which dispute if this is fair: this is an IPC test, not an instruction efficiency test. The DRAM official support is part of the hardware specifications, just as much as the size of the caches or the number of execution ports. Running the two CPUs at the same DRAM frequency gives an unfair advantage to one of them: either a bigger overclock/underclock, and deviates from the intended design.

So in our test, we take the new Ryzen 7 2700X, the first generation Ryzen 7 1800X, and the pre-Zen Bristol Ridge based A12-9800, which is based on the AM4 platform and uses DDR4. We set each processors at four cores, no multi-threading, and 3.0 GHz, then ran through some of our tests.

For this graph we have rooted the first generation Ryzen 7 1800X as our 100% marker, with the blue columns as the Ryzen 7 2700X. The problem with trying to identify a 3% IPC increase is that 3% could easily fall within the noise of a benchmark run: if the cache is not fully set before the run, it could encounter different performance. Shown above, a good number of tests fall in that +/- 2% range.

However, for compute heavy tasks, there are 3-4% benefits: Corona, LuxMark, CineBench and GeekBench are the ones here. We haven’t included the GeekBench sub-test results in the graph above, but most of those fall into the 2-5% category for gains.

If we take out Cinebench R15 nT result and the Geekbench memory tests, the average of all of the tests comes out to a +3.1% gain for the new Ryzen 2700X. That sounds bang on the money for what AMD stated it would do.

Cycling back to that Cinebench R15 nT result that showed a 22% gain. We also had some other IPC testing done at 3.0 GHz but with 8C/16T (which we couldn’t compare to Bristol Ridge), and a few other tests also showed 20%+ gains. This is probably a sign that AMD might have also adjusted how it manages its simultaneous multi-threading. This requires further testing.

AMD’s Overall 10% Increase

With some of the benefits of the 12LP manufacturing process, a few editors internally have questioned exactly why AMD hasn’t redesigned certain elements of the microarchitecture to take advantage. Ultimately it would appear that the ‘free’ frequency boost is worth just putting the same design in – as mentioned previously, the 12LP design is based on 14LPP with performance bump improvements. In the past it might not have been mentioned as a separate product line. So pushing through the same design is an easy win, allowing the teams to focus on the next major core redesign.

That all being said, AMD has previously already stated its intentions for the Zen+ core design – rolling back to CES at the beginning of the year, AMD stated that they wanted Zen+ and future products to go above and beyond the ‘industry standard’ of a 7-8% performance gain each year.

Clearly 3% IPC is not enough, so AMD is combining the performance gain with the +250 MHz increase, which is about another 6% peak frequency, with better turbo performance with Precision Boost 2 / XFR 2. This is about 10%, on paper at least. Benchmarks to follow.

Improvements to the Cache Hierarchy: Lower Latency = Higher IPC Precision Boost 2 and XFR2: Ensuring It Hertz More
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  • jjj - Thursday, April 19, 2018 - link

    I was wondering about gaming, so there is no mistake there as Ryzen 2 seems to top Intel.
    As of right now, I don't seem to find memory specs in the review yet, safe to assume you did as always, highest non-OC so Ryzen is using faster DRAM?
    Also yet to spot memory letency, any chance you have some numbers at 3600MHz vs Intel? Thanks.
    Reply
  • jjj - Thursday, April 19, 2018 - link

    And just between us, would be nice to have some Vega gaming results under DX12. Reply
  • aliquis - Thursday, April 19, 2018 - link

    Would be nice if any reviewer actually benchmarked storage devices maybe even virtualization because then we'd see meltdown and spectre mitigation performance. Then again do AMD have any for spectre v2 yet? If not who knows what that will do. Reply
  • HStewart - Thursday, April 19, 2018 - link

    I notice that that systems had higher memory, but for me I believe single threaded performance is more important that more cores. But it would be bias if one platform is OC more than another. Personally I don't over clock - except for what is provided with CPU like Turbo mode.

    One thing that I foresee in the future is Intel coming out with 8 core Coffee Lake

    But at least it appears one thing is over is this Meltdown/Spectre stuff
    Reply
  • Lolimaster - Thursday, April 19, 2018 - link

    Intel 8 core CL won't stop the bleeding, lose more profits making them "cheap" vs a new Ryzen 7nm with at least 10% more clocks and 10% more IPC, RIP. Reply
  • HStewart - Thursday, April 19, 2018 - link

    I just have to agree to disagree on that statement - especially on "cheap" statement Reply
  • ACE76 - Thursday, April 19, 2018 - link

    CL can't scale to 8 cores...not without done serious changes to it's architecture...Intel is in some trouble with this Ryzen refresh...also worth noting is that 7nm Ryzen 2 will likely bring a considerable performance jump while Intel isn't sitting on anything worthwhile at the moment. Reply
  • Alphasoldier - Friday, April 20, 2018 - link

    All Intel's 8cores in HEDT except SkylakeX are based on their year older architecture with a bigger cache and the quad channel.

    So if Intel have the need, they will simply make a CL 8core. 2700X is pretty hungry when OC'd, so Intel don't have to worry at all about its power consuption.
    Reply
  • moozooh - Sunday, April 22, 2018 - link

    > 2700X is pretty hungry when OC'd
    And Intel chips aren't? If Zen+ is already on Intel's heels for both performance per watt and raw frequency, a 7nm chip with improved IPC and/or cache is very likely going to have them pull ahead by a significant margin. And even if it won't, it's still going to eat into Intel's profit as their next tech is 10nm vs. AMD's 7nm, meaning more optimal wafer estate utilization for the latter.

    AMD has really climbed back at the top of their game; I've been in the Intel camp for the last 12 years or so, but the recent developments throw me way back to K7 and A64 days. Almost makes me sad that I won't have any reason to move to a different mobo in the next 6–8 years or so.
    Reply
  • mapesdhs - Friday, March 29, 2019 - link

    Amusing to look back given how things panned out. So yes, Intel released the 9900K, but it was 100% more expensive than the 2700X. :D A complete joke. And meanwhile tech reviewers raved about a peasly 5 to 5.2 oc, on a chip that already has a 4.7 max turbo (major yawn fest), focusing on specific 1080p gaming tests that gave silly high fps number favoured by a market segment that is a tiny minority. Then what happens, RTX comes out and pushes the PR focus right back down to 60Hz. :D

    I wish people to stop drinking the Intel/NVIDIA coolaid. AMD does it aswell sometimes, but it's bizarre how uncritical tech reviewers often are about these things. The 9900K dragged mainstream CPU pricing up to HEDT levels; epic fail. Some said oh but it's great for poorly optimised apps like Premiere, completely ignoring the "poorly optimised" part (ie. why the lack of pressure to make Adobe write better code? It's weird to justify an overpriced CPU on the back of a pro app that ought to run a lot better on far cheaper products).
    Reply

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