Overclocking our Z790 APEX:
Choosing your DDR5 kit based on memory chips:
As was already the case with DDR4, if you want to clock your memory, certain brands will benefit from better potential. At present, the kits announced by the various brands benefit from either Micron, Hynix or Samsung chips. The latter two brands will be the most interesting. As you can see, our Corsair Dominator Titanium 7200 MT/s CL34 kit is equipped with Hynix chips. But beware, there are Hynix M-die chips, the first to arrive, but above all today there are Hynix A-die chips, which allow you to increase frequency more easily.
It’s hard to generalize, especially with the arrival of 2 x 24 GB kits, but in most cases, kits between 6,000 and 6,400 MT/s are Hynix M-die, and from 6,600 MT/s upwards, they’re almost all Hynix A-die. As you’ll have gathered, our kit is a model with A-die chips, which we hope will give us good overclocking performance.
Key DDR5 voltages:
For memory overclocking, there are 5 key voltages. These are the voltages that will have an impact on overclocking and therefore on frequency rise or timing tightness. These are the CPU System Agent Voltage (SA), the DRAM VVD Voltage, the DRAM VVDQ Voltage, the Memory Controller Voltage and the IVR Transmitter VVDQ Voltage. Here’s where to find these voltages in the BIOS of our ROG Maximus Z690/Z790 APEX.
Please note that, depending on the type of memory chip (Micron, Hynix and Samsung), the balance between these different voltages is different. Don’t panic, we’ll come back to this in detail in our guide to overclocking Alder Lake and DDR5. If your PMIC module is not locked, by activating ” High DRAM Voltage Mode “, you’ll have access to voltages down to 2 volts. Now it’s time to overclock this Corsair DDR5.
Step 1: change processor and motherboard
What’s the point? Quite simply because the IMC(Integrated Memory Controller) on my 13900KS is much better than the one on my 12900K. Now integrated into the processor, the IMC enables faster, more direct RAM management than when memory controllers were on the motherboard. As with overclocking, there is a “lottery” and some processors benefit from a better IMC, enabling them to support higher memory frequencies. Since overclocking is all about increasing frequency, we might as well go for the best CPU at this game.
We’re also going to run another performance test with XMP profiles at 6400 MT/s and our i9-13900KS on this APEX Z790, so as to have a basis of comparison for our overclocking results. Here, we’ll test the potential of overclocking only on the AIDA64 memory benchmark and Geekbench 3.
Step 2: baseline scores on the APEX Z790 with the 13900KS
Let’s start with a benchmark score. This is very important, as it will enable us to judge the gain of our various modifications. When you need to fine-tune your overclocking, don’t modify several subtimings at the same time, as you may not know which one is the problem if your configuration isn’t stable.
Now that we’ve got two reference scores, we can start overclocking! You’ve probably already noticed that the scores are much better with the APEX Z790 combo and the i9-13900KS.
Step 2: profiles available in BIOS 0804
Head for BIOS 0084 of our APEX Z790 to see which profiles might be of interest to us. There are two of them, one at 7600 MT/s CL36 and the other at 8800 MT/s CL36. While the first seems fairly accessible, the 8800 MT/s profile seems complicated. That’s what we’re going to find out.
We load the BIOS and don’t forget to change the memory frequency, which doesn’t happen automatically. Let’s go for an AIDA64 and our traditional Geekbench3. Just as we’d imagined, there are no worries about stability, and performance is on the up! The good news about this profile is that it also requires a voltage of 1.40 volts.
As you can see, the gains are enormous, and it would be a shame not to take advantage of this performance boost thanks to the profile of our Z790 APEX, but also, and above all, thanks to the Hynix A-die chips that equip our Lexar ARES RGB 6400 MT/s CL32 memory kit.
And the 8800 MT/s profile? Well, just as we thought, impossible to boot. Even at 8600 MT/s, it’s not stable, so we opted for 8400 MT/s, lowering the Memory Controller voltage from 1.55 volts to 1.50 volts for stability.
Here again, the gain is very significant, as you’d expect. As for voltages, they are also 1.61 volts for the VDD and 1.59 volts for the VDDQ. These are higher voltages that can be used for benchmarks. For H24, we recommend not exceeding 1.50 volts. I think the performance speaks for itself, and we can’t help but be fully satisfied with the performance obtained with this Lexar ARES RGB 6400 MT/s CL32 kit, which, let’s not forget, is available for 123 euros!
