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Overclocking Tips and Tricks
Spoiler: Intel DDR5 Tweaking
With testing out of the way, it is time to see if this memory kit has any additional headroom. For Intel, we start off by using the XMP profile and increasing the frequency until the loss of system stability. After finding what can be accomplished without changing any of the timings or voltages, the second step can begin. This is where we go for the maximum frequency and lowest possible timings. Voltage modification above the XMP profile is allowed. After all, this is overclocking!
Intel's 11th Gen Intel Core processor paved the way for things to come. The introduction of the memory controller Gear Ratio allowed the system memory to run in synchronous 1:1 mode (Gear 1) with the CPU memory controller, or in a 2:1 ratio (Gear 2). With the release of Intel's 12th Gen Alder Lake based processors came DDR5 support and the additional 4:1 ratio (Gear 4).
It is generally considered that between 3600 and 4000 MT/s is the upper limit for Gear 1 support when using a Alder Lake (12th Gen Intel) CPU. This of course is partially dependent on the CPU memory controller and supporting voltages related to memory. In rare instances, higher-end motherboards can increase this slightly and offer better overall compatibility due to shorter trace length, higher PCB layer count and a better memory training algorithm. For instance the Intel Core i9-12900K used for these memory reviews maxes out at DDR4 4133 MT/s for single-rank memory. Achieving 4133 MT/s is quite a unlikely occurrence judging based by the sheer number of forum posts of many users struggling to get 3800 MT/s stabilized. It is safe to say that anything greater than 3600 MT/s using Gear 1 will often require a bit of hands-on tuning.
Since DDR5 has a higher operating frequency and a dual 32-bit data bus, synchronously operating it in 1:1 does not function at all. So far there have been no confirmed reports of this working for DDR5. That only leaves 2:1 Ratio and above as a viable option for any DDR5-based setups. The motherboard should automatically switch to the 2:1 ratio for both DDR4 and DDR5 above 3600 MT/s. If all else fails, you can manually enforce Gear ratios in the BIOS as well. With this information on hand, we can deduce that Intel 12th generation processors using DDR5 in theory will benefit the most from the highest-possible frequency, until the 2:1 ratio is not longer possible. At that point the cycle starts over again with a new 4:1 ratio and even higher frequency system memory.
Those looking to overclock on a Intel platform will generally find a hard barrier around 6600 MT/s using Intel Z690 and Intel 12th Gen CPU. Switching to Intel 13th Gen, this value increases to 6800-7200 MT/s when using Intel Z690 motherboards and 7800-8000 MT/s for Intel Z790 4-slot motherboards. Special overclocking specific motherboards like ASUS Z690 Apex, Gigabyte Z690 Tachyon, MSI Z690 Unify-X, ASRock Z690 AQUA OC, and EVGA Z690 Dark can reach up to DDR5-8000+. While the new wave of Z790 versions start at DDR5-8000 and can reach up DDR5-9000+ with exotic cooling such as LN2.
Caution is advised when raising 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 (VDD2), System Agent (SA), and VDDQ_TX voltages above Intel specifications 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 simply taken from screenshots posted on Discord or Reddit.
Getting Warm?
For thermal testing, Karhu stress test software was used for 30 minutes, after which both DIMM temperatures from the SPD hub sensors are averaged together. Testing was performed with and without a fan at the XMP Profile of 1.40 V. DDR5 SK Hynix memory ICs are susceptible to temperature related system errors. Since more voltage is necessary for higher frequency memory, caution is advised when overclocking without direct airflow across the memory, or at least decent case airflow. Otherwise, unexpected stability issues may occur as the memory warms up.
Tighter sub-timings and longer cell refresh cycle errors will greatly depend on the memory temperature as well. This is why retail kits generally have looser timings to account for different operational environments. It is recommended to stay below 60°C for 7200 MT/s. As while this memory kit did "pass" the 30 minute mark, the system froze shortly after and hard-locked at 70°C.
Note: 2-DIMM ASUS Z790 APEX was used. Due to close proximity, temperatures are 10°C higher compared to 4-Slot spacing without airflow.
Intel Results
DDR5-7800 Submission Link
DDR5-8000 Submission Link
DDR5-8200 Submission Link
For starters, overclocking with memory that uses SK Hynix A-Die IC was an interesting adventure to say the least. Every A-Die has different limits too. With only five kits on hand, it is hard to give a average limit of what A-Die can achieve for daily use, though they all can do 7600 MT/s at least. That being said, a direct fan on the memory is absolutely required for anything that is remotely memory intensive. There is a direct correlation to system stability and DRAM temperature. Lower is better and 45°C is the target goal. Contrary to what many preach on the forums, maxing out the DDR5 tREFI value is not ideal without proper cooling such as a waterblock at these higher memory frequencies. Longer delays between cell refresh cycle, can lead to stability issues and lost data. Therefore, all overclocking was preformed using a spare OS, that if corrupted would not hinder the review process.
After the first overclocking round with the
G.SKILL Trident Z5 RGB 6800 kit previously reviewed, it was time to push the limits some more. Now with a ASUS Z790 APEX motherboard in hand, it was time risk instant death of the memory (which didn't happen). Two things came out of that. One, this memory is completely stable at 8200 MT/s, and two, 8400 MT/s works to some extent.
As discussed already, memory temperatures are a big factor for a successful overclock, which could be resolved by using a waterblock or a direct fan. To achieve 8200 MT/s, the voltage had to be bumped up to 1.55, which is currently up for debate if that this okay for long term daily or not. Most will lend toward no, myself included, but it lasted 6 hours - all the way through the entire overclocking session. That is considered a win, though this does mean 8000 MT/s would be more or less the limit for this particular kit without exceeding 1.5 V. This particular kit did also need 1.5 V for 7800 MT/s, which means it would not have passed G.SKILL retail binning process. Thus, probably why it is binned and sold as a 7200 MT/s kit instead.
Note: All memory overclocks passed Karhu stress test 2000% or more.
Overclocking to these speeds is more about saying you can do it, because the benefits start to wane quite quickly beyond 7200 MT/s. For gaming, the RTX 3080 Ti was the limiting factor here. Using the ASUS Z790 APEX, DDR5-7800 overclock setup was simple and just required the correct DRAM voltage and primary / sub-timings timings, which the SPD data used was copied directly from another DDR5-8000 kit. Not really a challenge per say. 8000 MT/s and above is going to be a time sink. No overclock is ever guaranteed, which makes memory overclocking a new adventure every single time.