A basic question re: RAM overclocking

[LeadMagnet]

Hi all,

I'm in final stages of planning a new build and had a basic RAM / Mobo compatibility question with respect to overclocking. 

 

I've already decided on an Asus TUF Gaming B550M-PLUS Micro ATX for the motherboard, which is quoted as supporting (among others):

DDR4 4800(O.C.) / 4600 (O.C.) / ...... / 3466 (O.C) / 3333 (O.C.) / 3200 / 3000 / 2800 / 2666 / 2400 / 2133 MHz.

 

The question I have is whether the (O.C.) indicator always indicates frequencies that are only achievable through manual overclocking, or whether some of these frequencies over 3200 could still be met simply by setting the XMP profile?

Example: If I purchased some 3466 MHz and switched on the XMP profile, would I only hit 3200 MHz without doing further manual overclocking?

 

The reason I ask is that I'm not particularly interested in the nuts and bolts of overclocking so have assumed that I may as well just pick up the highest frequency non-O.C. listed frequency from the spec sheet, but I may be misunderstanding how this works.

 

Thanks in advance.

[Eigenvektor]

5 minutes ago, LeadMagnet said:

The question I have is whether the (O.C.) indicator always indicates frequencies that are only achievable through manual overclocking, or whether some of these frequencies over 3200 could still be met simply by setting the XMP profile?

Technically an XMP profile is also overclocking, you just don't have to specify the frequencies/timings yourself. The manufacturer of the RAM stick basically includes the tested/working settings for this stick as a profile. Anything that is outside the JEDEC specification (>3200 MHz) is an overclock.

[LeadMagnet]

6 minutes ago, Eigenvektor said:

Technically an XMP profile is also overclocking, you just don't have to specify the frequencies/timings yourself. Anything that is outside the JEDEC specification (>3200 MHz) is an overclock.

Ah! Thank you. So the XMP profile config at bios could also be used to hit those higher listed O.C. frequencies without requirement for more complex fine-tuning, then. That's great.  (While I'm not about to start pricing out 4800 Mhz sticks, it's nice to know I shouldn't outright rule out other frequencies above 3200.)

[Chris Pratt]

2 minutes ago, LeadMagnet said:

Ah! Thank you. So the XMP profile config at bios could also be used to hit those higher listed O.C. frequencies without requirement for more complex fine-tuning, then. That's great.  (While I'm not about to start pricing out 4800 Mhz sticks, it's nice to know I shouldn't outright rule out other frequencies above 3200.)

FYI, for best performance RAM clock needs to be the same as the infinity fabric clock (FCLK). On Zen 2, it maxes out at 1800MHz and on Zen 3, it can usually hit 1900MHz. It's possible, depending on the chip, to overclock the FCLK, but usually not that much. That makes 3600MHz the sweet spot (DDR means double data rate, so the real clock  3600MHz is actually 1800MHz - 2x1800=3600). You can potentially use as high as 4000MHz on Zen 3, if you can push the FCLK that high. Anything higher, or anything higher than what you can get the FCLK to match, will actually *hurt* your performance, as the chip will have to switch to a 2:1 ratio, halving your effective RAM speed. In other words, if you try to run at 4000MHz, but let's say the FCLK isn't stable above 1900MHz, then it will actually downclock itself to 1000MHz, and it will be effectively as if you were running 2000MHz RAM, obviously very slow for DDR4.

[LeadMagnet]

@Chris Pratt That's incredibly helpful, thanks very much.

[Guest]

1 minute ago, LeadMagnet said:

@Chris Pratt That's incredibly helpful, thanks very much.

If it where accurate assumptions, perhaps it could be of help.

 

IF does not impact memory performance. 

 

This thread, pay attention to George and his comments about IF. A small back and forth actually with one of our other team members that happens to be in house here at LTTF, I will mention him so he can give you the experience.

@freeagent

 

https://warp9-systems.proboards.com/thread/1514/help-get-ryzen-feet-wet?page=3

[Chris Pratt]

2 minutes ago, LeadMagnet said:

@Chris Pratt That's incredibly helpful, thanks very much.

No problem. It's one of those hidden gotchas with Zen because of the CCX design. For Intel, it's pretty much the faster the better with diminishing returns as you go higher. Ryzen is dependent on the infinity fabric for communication between the CCXs, so having too low a RAM speed actually slows down your CPU, because it slows down that communication layer, while too fast also works against you because of the need to stay 1:1. That's why you should always basically use the RAM speed that matches the maximum the FCLK can hit, anything more or less hurts performance.

[Chris Pratt]

8 minutes ago, ShrimpBrime said:

If it where accurate assumptions, perhaps it could be of help.

 

IF does not impact memory performance. 

 

This thread, pay attention to George and his comments about IF. A small back and forth actually with one of our other team members that happens to be in house here at LTTF, I will mention him so he can give you the experience.

@freeagent

 

https://warp9-systems.proboards.com/thread/1514/help-get-ryzen-feet-wet?page=3

Exactly what do you think is inaccurate? I didn't say it impacted memory performance. I said it "effectively" does. Your RAM is still 4000MHz, but the IF hits then every other cycle, so it's effectively the same as slotting in 2000MHz. That's just fact.

 

[Guest]

9 minutes ago, Chris Pratt said:

Exactly what do you think is inaccurate? I didn't say it impacted memory performance. I said it "effectively" does. Your RAM is still 4000MHz, but the IF hits then every other cycle, so it's effectively the same as slotting in 2000MHz. That's just fact.

 

The IF is the interconnect between CCX. Does not effectively do anything to or against memory frequency or the performance of it.

 

The memory controller is not dependant to IF frequency unless you absolutely feel the need to keep 1:1 ratio, which is not necessary or required to run high frequency memory on Ryzen chips.

 

Zen and Zen+ had a locked ratio and is the only 2 generations impacted by not having user intervention to uncouple the IF link.

[Nathanpete]

1 hour ago, Chris Pratt said:

-snip-

On Zen 2, it maxes out at 1800MHz and on Zen 3, it can usually hit 1900MHz. It's possible, depending on the chip, to overclock the FCLK, but usually not that much. That makes 3600MHz the sweet spot (DDR means double data rate, so the real clock  3600MHz is actually 1800MHz - 2x1800=3600). You can potentially use as high as 4000MHz on Zen 3, if you can push the FCLK that high. 

-snip-

I know 1800 MHz is still the sweet spot and usuall covered under warranty up to 1800 MHz, but I thought it was also not uncommon to actually hit 1933 MHz (or 3866 MHz) on the FCLK. Of course not everyone can even hit 1900 MHz, but I feel like if you wanted to really overclock, you could just buy a 3866 Kit and try to OC it above 3900 MHz. 3800 Kits were probably really close to validating at 3866 Mhz, so I feel like just getting a 3866 kit is better because you start off at a better validation point. 

 

That was a jumbled mess of words but I hope that made sense. Correct me if I'm wrong. 

[freeagent]

If you are running high fclk and you run out, but still have room with your ram, you can uncouple, and suffer a 7ns or so penalty.. I think.. its not as harsh as it was with Matisse.. at least in my limited experience. I can uncouple and still keep my latency under 60ns.. but you really gotta let the machine stretch its legs to do it..

 

As for that back and forth.. ehh.. I do lack people skills at times..

 

I could demonstrate later, right now home school with my two boys.. its like a real job lol.. teachers.. are awesome.

[Chris Pratt]

27 minutes ago, Nathanpete said:

I know 1800 MHz is still the sweet spot and usuall covered under warranty up to 1800 MHz, but I thought it was also not uncommon to actually hit 1933 MHz (or 3866 MHz) on the FCLK. Of course not everyone can even hit 1900 MHz, but I feel like if you wanted to really overclock, you could just buy a 3866 Kit and try to OC it above 3900 MHz. 3800 Kits were probably really close to validating at 3866 Mhz, so I feel like just getting a 3866 kit is better because you start off at a better validation point. 

 

That was a jumbled mess of words but I hope that made sense. Correct me if I'm wrong. 

You're correct. Many Zen 2 chips can overclock the FCLK that high, but it's also just as possible that you won't get a MHz over 1800. 3600 strikes a good balance of being fast enough without risking it being a waste or having to fiddle around a bunch in the BIOS to make it work, i.e. for people that just want things to just work.

[Chris Pratt]

1 hour ago, ShrimpBrime said:

The IF is the interconnect between CCX. Does not effectively do anything to or against memory frequency or the performance of it.

 

The memory controller is not dependant to IF frequency unless you absolutely feel the need to keep 1:1 ratio, which is not necessary or required to run high frequency memory on Ryzen chips.

 

Zen and Zen+ had a locked ratio and is the only 2 generations impacted by not having user intervention to uncouple the IF link.

Not sure if I'm not being clear or not, but we're talking in circles. I'm not talking about the RAM specifically. The RAM does what the RAM does and the IMC of course can handle those speeds usually with no issue.

 

I'm talking about the overall performance of the CPU and RAM together. Yes, you can run 2:1, but that literally means you halving the communication speed. Regardless of how fast the RAM is, you're only getting half the effective performance out of it at that point.

[freeagent]

Depends on how fast you can run your if to make up the difference.. 

[Guest]

2 hours ago, Chris Pratt said:

Not sure if I'm not being clear or not, but we're talking in circles. I'm not talking about the RAM specifically. The RAM does what the RAM does and the IMC of course can handle those speeds usually with no issue.

 

I'm talking about the overall performance of the CPU and RAM together. Yes, you can run 2:1, but that literally means you halving the communication speed. Regardless of how fast the RAM is, you're only getting half the effective performance out of it at that point.

Ah, gotcha. I understand better now.

This may be true for strictly speaking CCX performance while chips with only 1 should not see too much loss in performance. 

 

[Beerzerker]

8 hours ago, LeadMagnet said:

Hi all,

I'm in final stages of planning a new build and had a basic RAM / Mobo compatibility question with respect to overclocking. 

 

I've already decided on an Asus TUF Gaming B550M-PLUS Micro ATX for the motherboard, which is quoted as supporting (among others):

DDR4 4800(O.C.) / 4600 (O.C.) / ...... / 3466 (O.C) / 3333 (O.C.) / 3200 / 3000 / 2800 / 2666 / 2400 / 2133 MHz.

 

The question I have is whether the (O.C.) indicator always indicates frequencies that are only achievable through manual overclocking, or whether some of these frequencies over 3200 could still be met simply by setting the XMP profile?

Example: If I purchased some 3466 MHz and switched on the XMP profile, would I only hit 3200 MHz without doing further manual overclocking?

 

The reason I ask is that I'm not particularly interested in the nuts and bolts of overclocking so have assumed that I may as well just pick up the highest frequency non-O.C. listed frequency from the spec sheet, but I may be misunderstanding how this works.

 

Thanks in advance.

I'd research this before buying any RAM. 
TBH that board model, although it says it supports RAM of certain PC ratings may not be able to actually run it at those speeds.
I can use my Z270 Maximus IX Hero as an example - It "Supports" RAM speeds up to 4133 according to it's description/specs yet nearly all of those boards will not run RAM much above 3600 and it's a thing with that model.

What I'm saying is check to see what RAM speeds others are getting reliably from that board model before buying any RAM so you don't have disappointment and headaches trying to figure out why it won't run your RAM at it's full rated speed later. Get what it's been proven capable of running in terms of PC rating/speed so you don't buy a more expensive set only to come up short.
Good luck!

[freeagent]

10 hours ago, freeagent said:

I could demonstrate later,

Whoops I forgot you can keep it under 60ns with 2k fclk. 

 

 

Edit:

 

I should have run it, but if you run say 2100 fclk and run you ram that fast you will be in the 60k+ area for sure on reads and copies. I am back to four sticks so I can’t get over 1900 right now. I gotta whip it a bit to go that high with dual rank.

 

One more edit:

 

4x8