Does the DDR5 RAM fit?

Hello

The RAM fits on the motherboard, but there is no guarantee that the processor will work with it, with XMP enabled and at 6400MT/s memory speed.

Explanation: (if you are interested in why this is so)

The achievable memory speed no longer depends solely on the motherboard and the RAM modules, as it used to, but also, to a large extent, on the processor.

But first things first. Let's start with the motherboard and then slowly work our way to the processor.

According to the motherboard specifications of the specified Intel Socket 1700 Z790 motherboard, the BIOS/UEFI of the motherboard can manage the following memory capacities and set the following memory speeds on the memory controller:

https://rog.asus.com/de/motherboards/rog-strix/rog-strix-z790-f-gaming-wifi-ii/spec/

4 x DIMM slots, Max. 192GB, DDR5

8000+(OC)/7800(OC)/7600(OC)/7400(OC)/7200(OC)/7000(OC)/6800(OC)/6600(OC)/6400(OC)/ 6200(OC)/ 6000(OC)/ 5800(OC)/ 5600/ 5400/ 5200/ 5000/ 4800 Non-ECC, Unbuffered Memory*"

Dual Channel Memory Architecture

Supports ^Intel® Extreme Memory Profile (XMP)

OptiMem II

ASUS Enhanced Memory Profile II (AEMP II)

Supports DIMM Flex

• (OC) = overclocking

The information in the motherboard specifications are, as is often mistakenly assumed, not guaranteed achievable memory speeds, but only states which memory speeds can be set on the memory controller by the BIOS/UEFI of the motherboard, including the memory speeds that can only be achieved by overclocking the memory controller. There is nothing more to it.

Memory speeds that can only be achieved via overclocking are usually marked in the motherboard specifications as follows: (OC), (OC), (by A-XMP OC Mode) or (EXPO)

Therefore, the information in the motherboard specifications does not mean that the memory controller must automatically run at all adjustable memory speeds, especially not at the memory speeds that can only be achieved by overclocking the memory controller.

The memory controller is now located in the processor, not somewhere on the motherboard or in the RAM modules. And the memory speed is now set by the BIOS/UEFI, not somewhere on the motherboard or on the RAM modules themselves. The memory clock speed is then determined by the number of RAM accesses per second. Otherwise, the RAM itself isn't clocked and doesn't run at any speed on its own. Therefore, it's the processor, not just the motherboard and RAM modules, that is largely responsible for the actual achievable memory speed.

However, the RAM modules themselves must also be able to keep up with the memory speed set on the memory controller. They must therefore also be designed for the memory speed set on the memory controller. This is determined by the memory profiles that come with the RAM modules, and according to these profiles, the memory controller in the processor used is configured by the BIOS/UEFI.

These memory profiles also include XMP, or more recently, EXPO on DDR5 platforms. XMP or EXPO is provided by XMP or EXPO overclocking RAM modules and can then be selected and enabled in the BIOS/UEFI. These RAM modules are then overclocked to their intended speed via XMP or EXPO. However, the memory speed is also set on the memory controller in the processor, not on the RAM modules themselves.

The memory controllers in the Intel Socket 1700 processors that are compatible with this motherboard are designed for the following memory speeds, which can also be found in the specifications of the respective processor.

• Socket 1700 12xxx CPU – up to DDR4-3200 or DDR5-4800 RAM
• Socket 1700 13xxx i3/i5 without K/KF CPU – up to DDR4-3200 or DDR5-4800 RAM
• Socket 1700 13xxx i5 K/KF and i7/i9 CPU – up to DDR4-3200 or DDR5-5600 RAM
• Socket 1700 14xxx i3/i5 without K/KF CPU – up to DDR4-3200 or DDR5-4800 RAM
• Socket 1700 13xxx i5 K/KF and i7/i9 CPU – up to DDR4-3200 or DDR5-5600 RAM

The motherboard determines whether DDR4 or DDR5 RAM can be used, depending on whether DDR4 or DDR5 RAM slots are available on the motherboard.

For memory speeds above this, which can then also be used with faster RAM modules, the memory controller in the processor used is also forced to overclock. This may work, but it is not guaranteed to work, and it will slightly reduce the lifespan of the overclocked components. This would then affect the memory controller, i.e., the processor, and the XMP overclocking RAM modules. The same applies to AMD EXPO RAM modules, which were introduced with the AM5 platform.

Furthermore, the maximum achievable memory speed decreases the more memory banks (rank) are used per memory channel. This is due to the increased load on the memory controller caused by more memory banks and the physical properties of the memory bus in the high-frequency range. In simple terms, higher memory speeds can be achieved with two RAM modules than with four RAM modules. This should be taken into account, especially when overclocking the memory.

However, a memory bank is not always the same as a RAM module. There are single-rank RAM modules, where one memory bank corresponds to a complete RAM module, and there are RAM modules that already contain two memory banks. These are called dual-rank RAM modules. A dual-rank RAM module behaves roughly like two single-rank RAM modules in a single-channel configuration.

It doesn't matter how high the memory speed can be set by the BIOS/UEFI of the mainboard, on the memory controller in the processor, and how high the memory speed the RAM modules are designed for, because if the processor doesn't play along with the MEM overclocking, then it's still a waste of time.

Whether and to what extent the memory controller in a specific processor can be overclocked cannot be predicted, as this depends on the individual characteristics of each processor, even within the same series. Some can do more, while others cannot. This means that even if MEM overclocking works for others, it cannot be concluded that it will work the same in every other case.

Although the motherboards have been successfully tested with the memory speeds specified in the respective specifications, and the RAM modules that met these requirements can now also be found in the Memory Support List (QVL) for the respective motherboard, the motherboard manufacturers use specially selected engineering sample processors for these tests. Processors for the consumer market generally do not, or only rarely, achieve these memory speeds, and there is no guarantee that they will with the RAM modules from the memory support lists. Even with these RAM modules, the specified memory speeds can only be achieved if the processor used supports them—that is the prerequisite.

If, for correspondingly fast RAM modules, a higher memory speed is set via XMP or EXPO than the processor natively supports, i.e. without overclocking the memory controller, and the computer then runs unstable or no longer starts at all after the XMP or EXPO has been activated by the RAM modules in the BIOS/UEFI, then the simple MEM overclocking via XMP or EXPO does not work because the settings through the XMP or EXPO are too much of a good thing for the processor.

In this case, you'd have to manually adjust the memory speed. There might be several XMP or EXPO memory profiles available, one of which might work. Otherwise, with XMP or EXPO enabled, you'll have to manually throttle the memory speed until the processor runs smoothly, or you'll have to adjust the memory speed, timing, and RAM module voltage entirely manually. Have fun with it.

Since overclocking, due to the higher clock speed and the associated increase in voltage of the overclocked components, increases the effect of electromigration, overclocked components age faster, which in this case would affect the XMP or EXPO MEM overclocked RAM and the memory controller in the processor. However, it's impossible to make precise predictions about this.

https://de.wikipedia.org/wiki/Elektromigration

Overclocking can also cause the computer to become unstable or even stop working altogether. See also:

https://www.heise.de/meinung/Bit-Rauschen-der-Processor-Podcast-Uebertakten-nuetzlich-oder-gefaehrlich-7464285.html?wt_mc=nl.red.ho.ho-nl-newsticker.2023-06-21.link.link

This is another reason why I advise against overclocking.

If you still want to try MEM overclocking, using memory speeds outside the CPU specifications, to use those memory speeds with correspondingly fast XMP or EXPO RAM modules, and possibly even with more than two RAM modules, then you are welcome to do so, despite all the problems that may arise. That is your decision, however, and not my recommendation.

Kind regards, computertom