Tweaking for Speed

With testing out of the way, I endeavored to see if these sticks have any headroom. For Intel, I kept the same procedure I have been using: I used the XMP profile and increased the frequency until the system lost stability. After finding that limit, I manually tweaked for the maximum frequency and lowest possible timings. Voltage modification from stock is allowed. After all, this is overclocking!

The 11th Gen Intel Core processor paved the way for things to come. With the introduction of the memory controller Gear Ratio, it allowed the system memory to run in a synchronous 1:1 mode with the CPU memory controller, or a 2:1 ratio. With the release of Intel's 12th Gen Alder Lake based processors came DDR5 support and the additional 4:1 ratio.

1:1 ratio generally falls between between 3600 and 4000 MT/s for Alder Lake CPUs. This is completely dependent on the CPU memory controller and supporting voltages. In rare instances, higher-end motherboards can increase this slightly and offer better overall compatibilty. My Core i9-12900K maxes out at 4133 MT/s, which is rare if going by the sheer number of forum posts about many struggling to reach 3800 MT/s. It is safe to say that anything greater than 3600 MT/s will require a bit of hands-on tuning.

With this information, Intel 12th Gen Alder Lake paired with DDR5 will gain the most from the highest-possible frequency without giving up the benefit of the increased bandwidth. Because DDR5 has a higher operational frequency and dual 32-bit data bus, synchronously operating it in 1:1 is unlikely. That only leaves 2:1 and above as a viable option for any DDR5-based setup. The motherboard should automatically switch to the 2:1 ratio. If all else fails, you can manually set this in the BIOS.

Those looking to overclock will generally find a hard barrier around 6600 MT/s on the Intel Z690 as many 4-slot motherboards do not support higher speeds. Only a handful of motherboards are designed to support 6666 MT/s and up. These are the ASUS Z690 Apex, Gigabyte Z690 Tachyon, MSI Z690 Unify-X, ASRock Z690 AQUA OC, and EVGA Z690 Dark.

Caution is advised for DRAM voltage over the rated XMP profile. Direct airflow or a waterblock may be necessary for long-term stability. This extends to the CPU as well. Raising the integrated memory controller voltage (vDD2), System Agent (SA), and VDDQ_TX may cause irreparable damage. Please proceed with care and do research before attempting this. Do not copy and paste values without understanding the impact first, especially if taken from screenshots posted on Discord or Reddit.

Intel Results

Using the Intel Core i9-12900K and ASUS ROG Z690 Hero motherboard, I tried a number of different parameters. First was to go up using the XMP profile without changing the values. I was able to stabilize 6600 MT/s. Minor adjustments to the System Agent (SA), vDD2 (memory controller), and TX VDDQ were needed. If the motherboard does not automatically set these, manual intervention is required.

The next step was to go down and tighten the timings using only 1.4 V. Because this is part of the XMP profile, there were no worries about voiding the warranty or premature failures. After playing around with it for a while, I settled on 5200 MT/s CL26 and 6000 MT/s CL30. Both passed stability tests.

In the final act, after being completely done with the memory, it was time to raise the voltage and see where it would go. Unfortunately, the ASUS Z690 Hero had issues with 6666 MT/s. As such, it was time to try the Gigabyte Z690 Tachyon. Being a 2-slot motherboard, my thought process was that it should allow for better overclocking, which turned out to be true. 7000 MT/s CL32 booted into Windows, but was unstable in tests. This seemed to be more of an IMC voltage issue. Being that I was unwilling to increase it further, the compromise was 6800 MT/s CL32. More can be done with higher voltages, but that may end in disaster.