Discussion Please Help Me Understand Memory Clock Speeds

[Jp42nca]

This topic is about ASUS ROG Strix ITX motherboards for a new build. I understand Memory Clock Speeds can differ but my lack of knowledge makes it harder to understand. The specs/info I'm referencing to are on Amazon. Memory Clock Speeds on these boards differ from 2133 Mhz to 7000Mhz. I understand that the Z-Series can be overclocked and the B-Series cannot.

Looking at doing an open air case with a Streacom DAXL Chrome and appearance along with how well it performs goes hand in hand. Looking at the Z690-i & Z790-i. The Z690-i was the flagship awhile back, but the Memory Clock Speed is 2133Mhz and the newer Z790-i Memory Clock Speed is 7000Mhz, quite a difference. The price difference is only $80 which really confuses me.

ASUS
B660-i Memory Clock Speed 6000Mhz DDR5 Overclock No N/A Release Date Jan 2022 (New Not Available, only Used)
B760-i Memory Clock Speed 3600Mhz DDR5 Overclock No $199.00 Release Date Jan. 2023
Z690-i Memory Clock Speed 2133Mhz DDR5 Overclock Yes $259.00 Release Date Oct. 2021
Z790-i Memory Clock Speed 7000Mhz DDR5 Overclock Yes $339.00 Release Date Oct. 2022

I purchased the B660i last Dec for $199.00. It's paired with a i7-12700k, I have been very pleased with the performance & its my work pc. I do extensive photo editing with multiple layers in Lr & Ps.

I really need someone to help me understand the differences in Clock Speeds. Is higher better? Thanks for reading...

 

[Skripka]

So....what you're calling memory clock speeds aren't exactly, even though they commonly are spoken of that way. The DDR speed reference properly they are mega-transfers per second.

RAM Memory Speeds & Compatibility

Better understand your computer's RAM speeds & the compatibility of different types of memory to work out how to get the most from your desktop or laptop.

www.crucial.com

Which really gets to be a rabbit hole...because today we have DDR5. AKA double x double x double x double x DDR. With all that doubling--you get drastically increased theoretical bandwidth--but latency can and does go way up. Which leads to a funny thing where for example mature(old) low-latency DDR4 is faster than brand-new DDR5 that has much higher latency. DDR2 for example has far far lower latency than brand new (high latency) DDR5 (like 6-10x depending on what number you look at), but because of extra doubling, the DDR5 has higher throughput.

The reason for the pricing the way it is...is because eventually economies-of-scale hit a wall where financially you can't make money selling it cheaper per chip. The same with anything--you cannot sell a product for a profit cheaper than the manufacturing inputs. You open a lemonade stand--you can't make money if your drink price is less than the cost of the lemonade powder and water and however-much you value your time.


The other problem...is that, for years now, memory can be sold that is faster than any CPU will ever be able to drive at the rated speeds. Because the memory-controller isn't infinitely scalable and eventually becomes unstable. DDR started hitting those problems in the DDR3 days. Odds are if you buy say DDR5 7000 you'll never be able to run those rated speeds. Odds are anything over DDR5 6000 or 6400, you will not be able to hit stable as a rule of thumb unless you get lucky. Because the memory itself isn't the limit--your memory controller, that today is located inside your CPU) is. You'd need a "golden" CPU chip, which there used to be web resellers that specialized in such things--buying loads of CPUs in bulk, binning them, and upcharging for the really good CPUs of a given brand and SKU.

 

[Jp42nca]

So....what you're calling memory clock speeds aren't exactly, even though they commonly are spoken of that way. The DDR speed reference properly they are mega-transfers per second.

RAM Memory Speeds & Compatibility

Better understand your computer's RAM speeds & the compatibility of different types of memory to work out how to get the most from your desktop or laptop.

www.crucial.com

Which really gets to be a rabbit hole...because today we have DDR5. AKA double x double x double x double x DDR. With all that doubling--you get drastically increased theoretical bandwidth--but latency can and does go way up. Which leads to a funny thing where for example mature(old) low-latency DDR4 is faster than brand-new DDR5 that has much higher latency. DDR2 for example has far far lower latency than brand new (high latency) DDR5 (like 6-10x depending on what number you look at), but because of extra doubling, the DDR5 has higher throughput.

The reason for the pricing the way it is...is because eventually economies-of-scale hit a wall where financially you can't make money selling it cheaper per chip. The same with anything--you cannot sell a product for a profit cheaper than the manufacturing inputs. You open a lemonade stand--you can't make money if your drink price is less than the cost of the lemonade powder and water and however-much you value your time.


The other problem...is that, for years now, memory can be sold that is faster than any CPU will ever be able to drive at the rated speeds. Because the memory-controller isn't infinitely scalable and eventually becomes unstable. DDR started hitting those problems in the DDR3 days. Odds are if you buy say DDR5 7000 you'll never be able to run those rated speeds. Odds are anything over DDR5 6000 or 6400, you will not be able to hit stable as a rule of thumb unless you get lucky. Because the memory itself isn't the limit--your memory controller, that today is located inside your CPU) is. You'd need a "golden" CPU chip, which there used to be web resellers that specialized in such things--buying loads of CPUs in bulk, binning them, and upcharging for the really good CPUs of a given brand and SKU.

Sorry for the late response, I just saw this morning where you answered my post while I was on sff. I'm suppose to get email notifications when someone replied but did not on yours, again apologies.

I very much appreciate your in depth explanation, I now have a better understanding. I will read over the info on the link you sent.

As for the boards I've realized you can't always go by the info specs on Amazon. In the past I have let them know when something was inaccurate. Went to Asus website to get correct info.

Thanks for your time to help me understand more about memory & clock speeds.