Overclock.net - An Overclocking Community - View Single Post - Theories on why the SMT hurts the performance of gaming in Ryzen and some recommendations for the future

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post #8 of (permalink) Old 03-03-2017, 11:58 AM - Thread Starter
CrazyElf
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I feel that apart from the issues I've raised, AMD's CPU is very well made.

Quote:
Originally Posted by AlphaC View Post

Great overview.

It's interesting that you suggest the OS should recognize it as a 2P 4 core rather than 8 core.

I hope by the time Ryzen 5 releases many of these issues are ironed out by motherboard manufacturers and RAM manufacturers. So far the only RAM company seemingly on top of the RAM issue is GSkill , their "solution" in the long term is to release AMD Ryzen specialized RAM in the form of Flare X.

If your reasoning is correct then the biggest improvement could come with greater support RAM speeds (due to the CCX's Infinity Fabric implementation). Earlier news suggested the Infinity Fabric would be faster : "The company declined to give data rates or latency figures for Infinity, which comes only in a coherent version. However, it said that it is modular and will scale from 30- to 50-GBytes/second versions for notebooks to 512 Gbytes/s and beyond for Vega." http://www.eetimes.com/document.asp?doc_id=1330981&page_number=2

IMO when you see Firestrike/Timespy benchmarks with the Ryzen 7 competitive with respect to i7-6900K & i7-7700k @5.1GHz, then that means it is a game optimization issue.

Also I realized the Stilt's reasoning of < 3.3GHz being optimal for these chips might mean we ought to be under-volting instead of overclocking. It certainly explains the clockrates on ryzen 7 1700 and Ryzen 7 1700X.


+Rep - that gets my thought juices going.

Yes, which reminds me.

Once the RAM fix is in order, it may be advisable to buy the top binned RAM and OC it (best timings/clocks you can get). There is probably more to gain on tight timings and high RAM clocks on Ryzen than Intel platforms. The reason is because the Intel platforms don't use their DRAM as the last level cache, while Ryzen does. Furthermore, because they don't, it means that memory bandwidth is not the bottleneck in most cases, whereas when communicating between 2 CCXs, the memory could be a bottleneck. Actually, a 2 DIMM board might be a potentially good idea on Ryzen for that reason (trace lengths and possibility for better OC).

The source of the Infinite Fabric 22GB/s was the PCGH.de review. Apparently they talked with AMD about this.

Also, seeing that there's not much OC headroom and you want to undervolt, there is little point in buying flagship motherboards with insane VRMs, unless of course you need the other features that said flagship motherboards offer. Maybe put the savings towards buying better binned RAM. The only case you may want to consider a flagship then might be if that board has the ability to clock RAM faster.

Perhaps AMD should also focus on releasing a better memory controller for Zen+, although with my Zen+ proposals, it won't be needed because there will be a faster last level cache.

Will update the OP on this.





I'm actually worried about what the Infinity Fabric could mean for Vega. Keep in mind the 22GB/s is not a lot at all.

Quote:
Originally Posted by Quantum Reality View Post

Excellent!

Also, some benches I've seen support the theory that disabling SMT will help gaming framerates in the interim while OS, BIOS and microcode patches get rolled out.


WE should see modest gains. Getting rid of the SMT will add a few percentage points (perhaps as much as 10%) and the RAM fixes will add another few percent. That should mostly close the gap with Intel.

The big thing that we need to do for the microcode (and the OS kernels) to do is to treat the CCXs as different CPUs. If we can get say, a 4 thread game to only use 1 CCX, the gap will disappear. In that case, we could even see AMD get the kinds of wins in games that it gets in workstation benchmarks.



Quote:
Originally Posted by Yukon Trooper View Post

Meh. Many gaming benchmarks show much less than 10% difference with SMT enabled/disabled. I don't think there's as much to gain there as people are hoping.

I also take issue with the GPU bottleneck argument. That may be true for average/max FPS, but for the all-important minimum FPS metric we'll likely see Zen destroyed as more in-depth gaming benchmarks come out.

System optimizations, BIOS updates, etc. are only going to get peoples' hopes up. AMD doesn't even really try arguing this point. AMD's main argument is game developers will start coding for Zen moving forward, but it will take at least 1-2 years before the market is semi-saturated with Zen optimized titles.



True, it's not a huge difference, but it counts for a lot of people. The optimal use of CCXs would also likely boost not just games, but also the workstation loads even more. If games with less than 4 cores kept their loads within 1 CCX, they'd be able to pull the kind of results on games than they do on workstations.

Keep in mind that at 1440p where things are GPUs and not CPUs become the bottleneck (save in CPU bottlenecked games like Total War games). That means that even this bottleneck will disappear and in the few games that there are CPU bottlenecks, the faster RAM along with better CCX management should mitigate those.

I do not believe that with the fixes I have proposed Zen will get destroyed - at the very least, my Zen+ proposals would lead to viable fixes for Zen+.
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