I need help understanding RAM

XFX vsynch · April 9, 2021

Hi All,

This might be a very generalized question but I need some help understanding RAM.

I build PC's as a small side thing to earn some money since I lost my job, and I want to give better products to my customers.

I feel I have a general understanding about RAM but I need to know how to chose the correct RAM set up depending on the CPU and motherboard.

The i9 9900K CPU for example says it's using 2666 memory type. So does that mean if I get a motherboard that supports upto 3200, and RAM at 3200 I won't be able to XMP it to 3200 ?

Another thing is channels, I don't get what determines the amount of channels. Please explain to me how RAM channels work and what determines it, how do I go about choosing RAM and motherboards when It comes to channels. Do I get 4*8gb to make 32 or do I get 2*16gb.

Real world example: I got the Asus prime B560 and i9 10900kf for a workstation build few weeks ago and I wanted to put in 64 GB and I put in 4*16 (crucial 2666 16gb) but I was not sure if that motherboard or CPU can use the quad channel setup that I put in or is it using 2 dual channels to read the 4 ram sticks.

Another instance is I put in 4*16 of 3200 RAM, but I could only XMP it to 3000(b460 & i7 9700).

I hope you guys understand what Im trying to get at.

Please feel free to ask any questions to help me understand.

This is the largest, PC tech community that I know of so I need your guidance.

Thank you in advance

WereCat · April 9, 2021

- If the CPU support DRAM speed up to X then that means that the CPU was validated to run with that memory speed. As long as it's a "K" CPU (9900k in this case) it supports overclocking so you can also run your memory at higher speed if you have also a motherboard that allows overclocking ("Z" class motherboard on Intel). So yes, you can run 3200MHz XMP memory if you get both the CPU and motherboard that allows you to overclock.

- Memory channels depend on the platform. Pretty much all mainstream consumer platform only support Dual Channel. So it does not matter if you get 4 sticks of RAM or 2 stick of RAM, you will only run them in Dual Channel anyways. Having more sticks of RAM will increase you memory RANK size, but that only increases your bandwidth very slightly. Just get as much DRAM as you need, having more of it won't be of any benefit.

- B460 motherboard does not really allow overclocking so that's why your XMP was limited. I know Intel allows overclocking the DRAM on both the "Z" and "H" class motherboards for their 11th gen but that's not the case for the older platforms.

- Also have in mind that the more RAM sticks you have, the more difficult it will be to run the XMP (especially if its a higher than 3200MHz speed) because more memory ranks put a lot more stress on the memory controller so it may be unstable without manual tweaking which pretty much means you need to know how to OC the DRAM yourself to fix it, or at least have the patience to learn so basics and fiddle in the BIOS. So if you want high speed RAM, stick to two memory sticks and get as much capacity as you need.

Skiiwee29 · April 9, 2021

<--Moved to CPUs, Motherboards, and Memory-->

XFX vsynch · April 9, 2021

3 hours ago, WereCat said:

- If the CPU support DRAM speed up to X then that means that the CPU was validated to run with that memory speed. As long as it's a "K" CPU (9900k in this case) it supports overclocking so you can also run your memory at higher speed if you have also a motherboard that allows overclocking ("Z" class motherboard on Intel). So yes, you can run 3200MHz XMP memory if you get both the CPU and motherboard that allows you to overclock.

- Memory channels depend on the platform. Pretty much all mainstream consumer platform only support Dual Channel. So it does not matter if you get 4 sticks of RAM or 2 stick of RAM, you will only run them in Dual Channel anyways. Having more sticks of RAM will increase you memory RANK size, but that only increases your bandwidth very slightly. Just get as much DRAM as you need, having more of it won't be of any benefit.

- B460 motherboard does not really allow overclocking so that's why your XMP was limited. I know Intel allows overclocking the DRAM on both the "Z" and "H" class motherboards for their 11th gen but that's not the case for the older platforms.

- Also have in mind that the more RAM sticks you have, the more difficult it will be to run the XMP (especially if its a higher than 3200MHz speed) because more memory ranks put a lot more stress on the memory controller so it may be unstable without manual tweaking which pretty much means you need to know how to OC the DRAM yourself to fix it, or at least have the patience to learn so basics and fiddle in the BIOS. So if you want high speed RAM, stick to two memory sticks and get as much capacity as you need.

Thank you for the very informative reply.

So if I'm talking about Intel CPU's the only limiting factor of memory XMP in respect to the CPU is the "K" and non "K" version, as in the K will allow me to activate XMP and the non K would not ?

For example if I have an i7 10700, this would not let me run the advertised 3600MHz XMP profile ?

WereCat · April 9, 2021

6 minutes ago, XFX vsynch said:

Thank you for the very informative reply.

So if I'm talking about Intel CPU's the only limiting factor of memory XMP in respect to the CPU is the "K" and non "K" version, as in the K will allow me to activate XMP and the non K would not ?

For example if I have an i7 10700, this would not let me run the advertised 3600MHz XMP profile ?

yes

it's a bit different since the 11th gen and there I am not sure if they are now allowing the OC of DRAM on non-K CPU's but I know that they now allow the DRAM OC at least on the cheaper "H" series motherboards.

Everything before 11th gen though you need both "K" CPUs and "Z" motherboards at the same time to OC the DRAM.