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, leaving all settings at their XMP defaults and then increasing the frequency until the system loses 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 that allows the system memory to run in a synchronous 1:1 mode with the CPU memory controller, or a 2:1 ratio. Intel 12th Gen Alder Lake brought DDR5 support along with an additional 4:1 ratio and continuing DDR4 support.

The 1:1 ratio generally stops between 3600 and 4000 MT/s for Alder Lake CPUs. My Core i9-12900K maxes out at 4200 MT/s, which isn't 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 in a 1:1 ratio configuration is completely dependent on the CPU memory controller.

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 it can provide. Because DDR5 generally has a higher operational frequency, synchronously operating it in 1:1 is unlikely. That only leaves 2:1 as a viable option for any DDR5-based setup. The motherboards should automatically switch to the 2:1 ratio. If all else fails, you can manually set this in the BIOS.

Intel Results

Using the Intel Core i9-12900K and ASUS ROG Z690 Hero motherboard, I was able to reach 6800 MT/s after some voltage adjustments to the System Agent (SA), vDD2 (memory controller), and TX VDDQ. While this was not entirely stable, it shows potential of what is to come in the future. For now, 6600 MT/s is the highest stable overclock on this kit so far.

Having found the upper limit of what I can accomplish currently, it was time to narrow down the timings on a more reasonable frequency. Through my on-going testing, I have found 6000 MT/s to be overall hassle-free on most motherboards, especially after updating the BIOS since stability issues are still being worked out. Therefore, I decided to start there and lower the timings. Overclocking DDR5 is still a new experience, and while I was able to bring it down to CL 36 without any additional voltage, CL 34 would only boot if 1.435 V was applied and never passed any stability tests. More tweaking can be done at CL36 if looking to get a bit more out of the memory kit.