Memory overclocking :
Well, let’s start with a theoretical reminder since there are some changes with the arrival of the ZEN 4 architecture as far as memory is concerned. While for the Ryzen 5000, the standard was to keep a 1:1:1 ratio between mclk:uclk:fclk, this will change with the Ryzen 7000. Indeed, these adopt DDR5 memory. The frequency of DDR5 memory is increasing, which means that the ratio will change. AMD now recommends for DDR5 motherboards a 1:1 ratio for the mclk:uclk and to finally leave the fclk in AUTO which will automatically set it to 2000 MHz. Theoretically, this is how it will behave:
- DDR5-4800 will give with the new ratios 2400:2400:2000 MHz (mclk:uclk:fclk)
- DDR5-5200 will work with the new ratios 2600:2600:2000 MHz (mclk:uclk:fclk)
- DDR5-6000 will work with the new ratios 3000:3000:2000 MHz (mclk:uclk:fclk)
Well, it may seem a bit complicated like that, but we’ll explain it all to you. First of all, don’t panic, if you activate your XMP or EXPO profile in the BIOS, everything will be set automatically. The explanations we give you here are for those who want to overclock their memory kit.
fclk, mclk, uclk, a little reminder:
The fclk is the frequency of the Infiny Fabric which can be, since the previous generation, controlled independently via the BIOS settings. By default, this value is set to AUTO and the motherboard will manage its frequency to ensure system stability. Its maximum frequency is around 2100/2200 MHz but it also depends on the quality of your processor, but that’s up to the lottery. The mclk, also sometimes called “memclk”, is the frequency of your memory kit and the uclk is the frequency of the memory controller.
Also be aware that if you exceed 6000 MT/s with your memory kit, automatically the memory controller (uclk) frequency will switch to a 1:2 ratio again to ensure system stability. AMD states that the best performing frequency and ratios are 3000:3000:2000 (mclk:uclk:fclk).
Let’s see what happens if we insert our Teamgroup Delta RGB 6600 MT/s CL34 kit. This is not an EXPO compatible memory kit and we will need to enable the XMP profile. We reboot the motherboard and … … impossible to boot with the XMP profile. In spite of several settings and even by opting for a uclk of half, nothing makes it. You should therefore be very careful when choosing and purchasing your memory kit. We can only advise you to opt for an EXPO compatible kit.
Memory overclocking via BIOS profiles:
This ROG Crosshair X670E Gene has several memory profiles in the BIOS depending on the type of chips in your memory kit. Here we know that on our GSKill kit, it is Hynix chips.
So there are two profiles that we can test. The first one goes through very easily and the second one needs, with our memory kit, a bit more voltage than expected. We had to increase the VDDQ voltage from 1.45 v to 1.5 v. Here are the benchmarks of these two profiles under Geekbench 3.4.4.
And finally, above, the table of the performance gain obtained thanks to these two profiles available in the BIOS.
As you can see, in the end, the two profiles offer almost the same performance. As you know, it is the memory overclocking that is the most delicate and we will see in the coming weeks how to improve on this point.