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Memory Frequency - Busting PC Building Myths!

27 Jan 2022

While Intel and the new 12th Gen processors have been in the spotlight for the past few weeks with their support for new kits of DDR5 memory, there is still a lot of confusion about how memory speeds are supported on the new platform. As many of you will be interested in the new DDR5 kits, let’s take a look at what memory speeds are supported on your platform of choice and clear up some confusion related to what speed memory will work with the rest of your hardware.

Memory frequency, also referred to as memory speed sometimes, is the number following the generation of RAM of your selected kit and is typically measured in megahertz (MHz). An example of this would be a 16GB kit of DDR4-3200. This refers to 16GB of DDR4 running at 3200 megahertz.

On a modern desktop computer, there are generally 3 components which affect the frequency that your memory will be able to run at. First is obviously the memory kit itself, second is the motherboard that you are installing the memory on, and finally there is the processor. The combination of these 3 components determines the frequency at which you can set your memory frequency to run at, but it becomes confusing as there are different specifications for each of these components.

Let’s say that you are a customer looking to purchase the best gaming PC today, and you are interested in the Intel Core i9-12900K processor paired with an ASUS ROG Maximus Z690 Apex motherboard and a shiny new kit of Corsair’s Dominator Platinum memory rated at 6200MHz. The first thing that you would have noticed is the memory kit rating of 6200MHz. This means that Corsair has tested the memory and can guarantee that the memory kit itself will not have problems running at 6200MHz. The second thing that most users will check is the motherboard for support running the memory at that speed. The ASUS specification for the Z690 Apex is a maximum memory speed of 6600MHz. The final but CRUCIAL component which you need for your memory to run at is the CPU, which is very often overlooked when running high-frequency memory.

The memory controller is the digital circuit on your processor that manages the flow of data between the processor itself, and the system memory (RAM). Prior to 2008, Intel CPUs shipped without a memory controller on the chip itself, leaving motherboard manufacturers to integrate this circuit into their motherboard designs. This meant that in the past, whatever the motherboard manufacturer rated their motherboards as supporting in terms of memory frequency was what you would have been able to run your memory kit at.

With modern desktop processors from BOTH AMD and Intel, the memory controller is now integrated into the CPU package itself, and is responsible for the frequency that the memory is able to stably run at. Generally memory speed isn’t one of the main specifications that Intel or AMD will list when showing off a new desktop or mobile processor, but if you do a little digging on the specification sheet for a processor you will be able to find a maximum supported memory specification. For the Core i9-12900K, this is up to DDR5-4800MHz, or DDR4-3200MHz. Just for reference, AMD desktop processors also have this specification listed i.e. Ryzen 9 5950X has support for up to DDR4-3200MHz.

What does this mean for you? Why does the manufacturer of the memory or motherboard list speeds which are much higher than the rated speed of the CPU? How does anybody get the DDR5-6200 and higher speed kits running with their 12th Gen CPU? The answer to this is overclocking. What most people do not realise, is that running their memory at a speed higher than the rated speed of the CPU whether that is through manual tuning or using something like an XMP profile for Intel based systems or D.O.C.P profile for AMD systems is that those are technically considered ‘overclocking’. Because they are running the memory at a frequency higher than what the CPU manufacturer states as the ‘maximum supported speed’, you cannot be guaranteed that the memory controller on the CPU will be able to handle the higher speeds. This is why not all 6200MHz and higher speed DDR5 kits will work properly even if the memory kit itself and the motherboard can support higher speeds. At the end of the day, the quality of the silicon which the memory controller is built on can determine the highest frequency that you will be able to achieve. Another thing to note is that the addition of more memory channels will also decrease the maximum speed that you are able to run memory at, as running more channels puts more load on the memory controller.

Generally speaking, as a platform matures over time then higher speeds will become more and more achievable as the silicon quality and yields get better. This can be seen on any older platform, such as the Ryzen line of processors. Initially, memory support was not very good, but over time as the technology became more mature then many users became able to run memory at high frequencies, and these days although DDR4-3200MHz is still the maximum supported memory on the AM4 platform, most people have no problems using DDR4-3600 or 3800MHz memory using the built-in memory profile. Shown below is a table of maximum supported memory speeds and channels for a range of processors including some from previous generations as a point of reference:

ProcessorDDR4 SupportDDR5 Support Maximum Channels
Intel Core i9-12900K (Launched Q4 2021)3200MHz4800MHz2
Intel Core i9-11900K (Launched Q1 2021) 3200MHzN/A2
Intel Core i9-10980XE (Launched Q4 2019)2933MHzN/A4
Intel Core i5-11600K (Launched Q1 2021)3200MHzN/A2
Intel Core i5-10400F (Launched Q2 2020)2666MHzN/A2
AMD Ryzen 9 5950X (Launched Q2 2020)3200MHzN/A2
AMD Ryzen 5 5600X (Launched Q2 2020)3200MHzN/A2
AMD Ryzen 5 1600 (Launched Q2 2017)2667MHzN/A2
AMD Ryzen Threadripper 3995WX (Launched Q3 2020)3200MHzN/A8
AMD Ryzen Threadripper 1950X (Launched Q3 2017)2667MHzN/A4

As you can see in the table above, the memory frequency has increased with DDR4 memory over time as the platforms have matured from 2666MHz with 10th Gen 10400F up to 3200MHz today with 12th Gen Core i9-12900K. If you are looking to build a new system, or want to upgrade your gear in an existing PC and are looking at memory that is rated for a higher speed than the CPU's supported maximum make sure to keep in mind that you may not always be able to hit the maximum rated speed of the memory. As always, our team here at Computer Lounge is available for more information in-store or online if you have any questions about memory, overclocking or any other PC hardware related info!


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