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Ryzen 3000 CPU's and fast ram

Knowing that the Ryzen 2000 CPU's liked fast RAM, What speed of RAM would you suggest for the new 3000's?  Your best guess of course.  I'm in the process of building a new PC and want to start buying parts when I see them on sale while I wait for Ryzen 3000.  Would I be ok with going with something like CORSAIR Vengeance RGB PRO 16GB (2x8GB) DDR4 3200MHz?

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2 minutes ago, FineVisionz said:

Knowing that the Ryzen 2000 CPU's liked fast RAM, What speed of RAM would you suggest for the new 3000's?  Your best guess of course.  I'm in the process of building a new PC and want to start buying parts when I see them on sale while I wait for Ryzen 3000.  Would I be ok with going with something like CORSAIR Vengeance RGB PRO 16GB (2x8GB) DDR4 3200MHz?

This will sound rude, but why are you talking about fast RAM and shopping for a 3200MHz kit?  Are there budget constraints?  

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Just now, nick name said:

This will sound rude, but why are you talking about fast RAM and shopping for a 3200MHz kit?  Are there budget constraints?  

My current build has 1600Mhz so 3200Mhz seemed quick.  I've been out of the loop for a while I guess, haha. 

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1 minute ago, FineVisionz said:

My current build has 1600Mhz so 3200Mhz seemed quick.  I've been out of the loop for a while I guess, haha. 

Ahhh, gotcha.  How much do you wanna spend?

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2 minutes ago, nick name said:

Ahhh, gotcha.  How much do you wanna spend?

No idea to be quite honest.  I could push it to $150ish maybe?  I've never thought of RAM as a "big performance" factor so I've never really paid that much to it before.

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16 minutes ago, FineVisionz said:

No idea to be quite honest.  I could push it to $150ish maybe?  I've never thought of RAM as a "big performance" factor so I've never really paid that much to it before.

Well I would try for the fastest you can afford with the lowest timings. 

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The new Ryzen 3xxx will work best up to 3600 Mhz. 

 

I've heard that if you go to or above 3800 Mhz, there's an internal 1:2 division when the data is moved into the Infinity fabric, so it actually takes double the amount of time... memory sticks running at 4000 mhz will behave as if they're 2000 mhz sticks.

 

Apparently it's possible to go up to DDR4-5000 but internally transfers will work as if you run the ram at 2500 mhz (2x1250 Mhz)

 

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28 minutes ago, mariushm said:

The new Ryzen 3xxx will work best up to 3600 Mhz. 

 

I've heard that if you go to or above 3800 Mhz, there's an internal 1:2 division when the data is moved into the Infinity fabric, so it actually takes double the amount of time... memory sticks running at 4000 mhz will behave as if they're 2000 mhz sticks.

 

Apparently it's possible to go up to DDR4-5000 but internally transfers will work as if you run the ram at 2500 mhz (2x1250 Mhz)

 

This is a poor explanation that kinda gets things right.  

 

 

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35 minutes ago, mariushm said:

The new Ryzen 3xxx will work best up to 3600 Mhz. 

 

I've heard that if you go to or above 3800 Mhz, there's an internal 1:2 division when the data is moved into the Infinity fabric, so it actually takes double the amount of time... memory sticks running at 4000 mhz will behave as if they're 2000 mhz sticks.

 

Apparently it's possible to go up to DDR4-5000 but internally transfers will work as if you run the ram at 2500 mhz (2x1250 Mhz)

 

 

5 minutes ago, nick name said:

This is a poor explanation that kinda gets things right.  

 

 

What? Why?

 

So I shouldn't go above my 3600mhz kit when I upgrade?

 

Seriously..?

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Yeah, seriously. The Infinity fabric which connects the 3 dies (2 x 8core + i/o die) just can't handle such high frequencies.

Added divider is compromise.

 

Note, you CAN get higher freq. sticks and run them at 3600 Mhz with lower timings.

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19 minutes ago, ch3w2oy said:

 

What? Why?

 

So I shouldn't go above my 3600mhz kit when I upgrade?

 

Seriously..?

The 3600MHz figure isn't the point where you have to de-couple Infinity Fabric -- that's at 3733MHz.  And I've seen some folks mention it may vary if you have a good CPU.  1usmus gave me that impression.  I think @mariushm was trying to say that 3600MHz is the AMD recommend price/performance speed.  

 

And for those that want faster than 3733MHz RAM; say 4000MHz, then you have to run asynchronous frequencies for RAM and Infinity Fabric.  But that doesn't mean your RAM is slower or runs like it's at half-speed -- it's the CPU's Infinity Fabric that is reduced.  That will increase latency, but not make RAM  behave as if it was running 2000MHz RAM.

 

I believe he was referencing a slide I'll post below.  And you can see the latency for 2667MHz RAM is still higher than the 4000MHz RAM that necessitates  the 2:1 ratio.  

Ryzen 2 Memory.png

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12 minutes ago, nick name said:

The 3600MHz figure isn't the point where you have to de-couple Infinity Fabric -- that's at 3733MHz.  And I've seen some folks mention it may vary if you have a good CPU.  1usmus gave me that impression.  I think @mariushm was trying to say that 3600MHz is the AMD recommend price/performance speed.  

 

And for those that want faster than 3733MHz RAM; say 4000MHz, then you have to run asynchronous frequencies for RAM and Infinity Fabric.  But that doesn't mean your RAM is slower or runs like it's at half-speed -- it's the CPU's Infinity Fabric that is reduced.  That will increase latency, but not make RAM  behave as if it was running 2000MHz RAM.

 

I believe he was referencing a slide I'll post below.  And you can see the latency for 2667MHz RAM is still higher than the 4000MHz RAM that necessitates  the 2:1 ratio.  

Ok ok.. That makes a little more sense.. Asynchronous separates the speeds right? Synchronous runs everything at the same speed? So you can still benefit from faster RAM, right?

 

I asked someone else but they never answered, do you think running a higher frequency (maybe 3733mhz) with looser timings, is better than lower frequency with tighter timings, for Ryzen?

 

14 minutes ago, mariushm said:

Yeah, seriously. The Infinity fabric which connects the 3 dies (2 x 8core + i/o die) just can't handle such high frequencies.

Added divider is compromise.

 

Note, you CAN get higher freq. sticks and run them at 3600 Mhz with lower timings.

I see.. You agree with Nick Name? So we're basically ONLY talking about infinity fabric right? RAM will still benefit from higher speeds?

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I agree with nick... we're both right in some ways.

For small data sizes, latency may matter and you can see in picture above latencies are tiny bit higher with divider..

Problem can be if  you do large transfers between ram and anything.

At 3600mhz you have 57 GB/s between ram and anything... but with 4000mhz you have now  infinity running at 2000 mhz so max ~ 32GB/s throughput between ram and everything(pci-e, usb, cores and L3 caches,etc)

In real world not much is gonna get close to 30GB /s to actually affect things, home  users don't deal with massive loads of data

But also ... it won't really benefit you in any way to go over 3600... you just waste money

 

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@ch3w2oy  Honestly, I'm not certain if speeds higher than 3600MHz can be run with lower timings.  Looking at what timings Intel guys run on their high speed kits makes me think we won't see the best performance with those speeds that have to run a 2:1 ratio since we will likely have to go higher than CAS latency 14.

 

11 minutes ago, mariushm said:

-snip-

At 3600mhz you have 57 GB/s between ram and anything... but with 4000mhz you have now  infinity running at 2000 mhz so max ~ 32GB/s throughput between ram and everything(pci-e, usb, cores and L3 caches,etc)

-snip-

 

I see what you mean now when you said "memory sticks running at 4000 mhz will behave as if they're 2000 mhz sticks".  It makes sense, but I'm hoping that isn't the case.  Was this something AMD described?

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On 6/13/2019 at 3:39 AM, mariushm said:

Yeah, seriously. The Infinity fabric which connects the 3 dies (2 x 8core + i/o die) just can't handle such high frequencies.

Added divider is compromise.

 

Note, you CAN get higher freq. sticks and run them at 3600 Mhz with lower timings.

Sorry to pick at this, but you wont be getting that triple die setup unless you spring for a Ryzen 9. The 7's would only have 2 making latency a smaller issue then it would have been otherwise.

 

I am also trying to consider what kind of memory to move to when I upgrade and I suppose the sweet spot as some would say is closer to that 3600MHz

Buildzoid Rambled about the whole situation in his X570 video a few hours ago. 

It's also just a general rule that if you want more capacity, you'll be having lower speeds if you don't want to break the bank, cause at $150 usd right now you can get a 3600MHz 2x16 kit, which still boggles my mind being someone who started their pc building whatever at the height of Crypto and RAM shortages 

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@mariushm Found some Geekbench 4 benchmarks.  The CPU speeds are slightly different so that makes comparing a little harder.  The biggest thing is we can see 3200MHz versus 4400Mhz with some actual data.  Not knowing timings sucks, but it's a start.

Edit:  Found a 4266MHz I linked.  

 

4400MHz:

http://browser.geekbench.com/v4/cpu/13526365

 

4266MHz:

http://browser.geekbench.com/v4/cpu/13512793

http://browser.geekbench.com/v4/cpu/13472133

 

3200MHz:

http://browser.geekbench.com/v4/cpu/13527784

 

My 3600MHz 14-15-14-14 and tight subs:

https://browser.geekbench.com/v4/cpu/13532495

AMD Ryzen 5800XFractal Design S36 360 AIO w/6 Corsair SP120L fans  |  Asus Crosshair VII WiFi X470  |  G.SKILL TridentZ 4400CL19 2x8GB @ 3800MHz 14-14-14-14-30  |  EVGA 3080 FTW3 Hybrid  |  Samsung 970 EVO M.2 NVMe 500GB - Boot Drive  |  Samsung 850 EVO SSD 1TB - Game Drive  |  Seagate 1TB HDD - Media Drive  |  EVGA 650 G3 PSU | Thermaltake Core P3 Case 

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Stock speed is 3200mhz. I think I'm gonna run that. Vengence lpx. Seems like the mhz increase vs timings isnt worth the money prob use the money saved for a 3900x and 32gig of ram. 

 

3800X, Corsiar 32gig 3200mhz LPX, Asus Hero X570. 2080ti black edition

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