Intel Memory Overclocking & Performance Tuning Guide

Part 2: Overclocking & Performance Validation

Preparation: The very first thing I advise you do, is locate your CLEAR_CMOS button on your motherboard (if you have one) or put your system in a location that adjusting your CMOS jumpers/battery is easily accessible. You are certainly going to be using them, no exceptions. Next be sure to have your power supply's power cable near you. Sometimes, removing this and holding down the power button for 60 seconds, results in enough of a clear to allow you to get back into BIOS without completely resetting everything. Lastly, save all of your "pseudo-stable" profiles, so that you can continue to adjust them for better stability without starting over.

It's important to keep in mind that the information provided below based on an ASRock board but is universally applicable to all Intel-based motherboards. The names of certain timings/settings might differ slightly, but their functions will be identical. If you have questions during this process, feel free to comment down below.

Overclocking Time!: Now that we have the preparations out of the way, it's time to start tinkering. I recommend focusing on Frequency first, while keeping your primary timings the same. I personally dial in a vDIMM of 1.35v, and then I start increasing my memory frequency one memory strap at a time. If I was at 3000 C15, I would try 3200 C15, then 3333 C15, 3466 C15, and so on. When you reach a point to where it no longer posts, you have 3 options. Option 1: Throw more voltage at it. Option 2: Loosen your primary timings. Option 3: settle for last bootable configuration. 

I advise trying option 1 first, as it might only take a little bit more vDIMM to make it stable. For example: My 3600 C14 profile is unstable at 1.35v, but stable at 1.39v. With modern XMP kits now launching at up to 1.5V on DDR4, this is still quite tame and most DIMM's will be perfectly fine with even bare minimum airflow at this voltage. Now, your VRM components near your ram on the motherboard, that's a different story entirely. Use common sense, and try to avoid going over 1.55v for 24/7 vDIMM and you should be fine.

Option 2 is what we call "compromising". You have to be careful when making compromises on timings for speed. The end must justify the means. If you gain a slight amount of bandwidth, but lose on latency at all, it's a bad trade. Memory is already so ridiculously fast in regards to bandwidth, that latency should ALWAYS come first in your mind. That being said, frequency can be just as good for latency as it is with bandwidth. It just takes a little balance. If you increase frequency while keeping timings the same, latency improves. If you loosen latency while increasing bandwidth, one of two things can happen:

1. You have faster bandwidth, and latency remains the same as a result. This is a good trade with no negative side effects, so I tend to allow this.
2. You gain bandwidth, but latency suffers. This is a terrible trade, and should never be made. Go back to your last configuration, and work on making that stable instead.

When making minor tweaks, I recommend using software like Aida64's memory bandwidth test (cachemem test) to see your gains in performance. Yes, I know it sucks using paid software, but it seriously helps with knowing whether or not your timings are making a positive or negative impact in performance.

If you choose not to purchase AIDA64 or do not see yourself using the features often, you can use the individual benchmarks on the left hand side to get an idea of how your memory is performing. Still, if you want to be serious about this, I strongly urge you to consider this software. Outside of memory overclocking it has other fantastic features and it never hurts to support software developers.

Now that we've gotten frequency and primary timings taken care of, it's time for secondary timings. While you will see small gains from most of these timings, I want to focus on one very important secondary timing. tRFC. You see, memory is a matrix of billions of capacitors that need to be recharged. You have tRFC, a secondary timing, that works alongside tREFI, a tertiary timing. Every <tREFI>, they are recharged in order, for <tRFC> amount of time. Simply put: tRFC is the amount of time your ram can do nothing, while being recharged. tREFI = the amount of time your ram can do things, before needing recharged. Both are very important, and have significant impact on your latency. tRFC works best as low as you can get it, and tREFI functions best as high as you can get it. tRFC, for most people, is best left at 270, as it's the easiest value to keep stable while having the best gains in performance. tREFI on the other hand, can go as high as 65535 and provide much lower memory latency, but can potentially lead to corruption if your motherboard's quality is lackluster. The warmer your DIMMS, the more often they need recharged. If motherboard is bad, it can't recharge high enough to meet the required interval. Basically, if motherboard is bad, stick to the JEDEC standard of 7.8usec refresh interval. If your ram is 3000mhz, the formula is 1500 x 7.8 = 11700. If your ram is 3600mhz, the formula would be 1800 x 7.8 = 14040 tREFI.

There are other formula's for your secondary timings worth following, such as: tFAW = tRRD x 4. The others, they tend to take trial and error. Gain's can be small, or big, depending on whether or not you are using DDR3 or DDR4. I can say that with DDR4, the gains are not as massive as touching tertiary timings. Speaking of which...

Tertiary timings. Depending on your level of masochism, this will be the part you love the most, or absolutely dread. There is no in-between. As you saw above during the terminology half, tertiary timings tend to have a few suffixes after their name. These are SG, DG, DD, and DR. As for DD, these are related to 2DPC (DIMMS Per Channel) and only matter if you have 2 DIMMS per channel (ITX users rejoice, less complication) while DR matters when using multi-rank kits. It's easier to associate DR with "Dual Rank". If you have a single rank kit, touching _DR timings does literally nothing. No positive or negative, and no instability issues either. I recommend taking these one at a time, or at the very least, one group at a time. Focus on tRDRD (and all of it's suffixes), followed by tRDWR, and so on. Fun fact about tRDWR: these timings directly impact AVX. The tighter they are, the hotter AVX is. The looser they are, the cooler AVX is. Those of you that fear AVX, you might be able to use this to your advantage, and make those stress tests easier on yourself. I promise not to judge you.

Once you've finally settled on your tertiary timings, and have gone through countless hours of stress tests, it's time for the bane of my existence. RTL/IO-L's. I honestly cannot give you any better advice, other than "You gotta feel it". There is no magical value that I can tell you to dial in, and have it work. RTL has one very specific value it likes, and a few others that it "tolerates", and that's it. Either it works, trains poorly, or doesn't work at all. Now, with DDR4, we do have a trick up our sleeves to at least prevent it from training poorly. It's a very simple formula for a specific setting called "RTL Init". This formula is: IO-L + IO-L Offset + CL (x2) + 10. Let's say your IO-L is 4, and your offset is 21. You have a CAS Latency of 14. The formula would be: 4 + 21 + 14 (x2) + 10 = 63. Once you input 63 in the RTL Init setting, your IMC will no longer train RTL's beyond it's current threshold. This is great, as it at least prevents performance from getting worse. However, this is only a band-aid. You should still strive to find optimal settings for RTL/IO-L. That being said, do not beat yourself up dwelling on this. If you've gained significant strides in all other aspects of your ram, then feel proud of what you've accomplished. It's still worlds beyond what XMP can offer you, and you've gotten one step closer to mastering one of the most difficult "overclocking disciplines" there is.

Part 4: Conclusion

I am hoping that this guide made sense and that it wasn't too difficult to follow. I know that reading through it can be pretty daunting especially with the large glossary of timings, voltages and general terminology but honestly you do not need to know what anything does in order to adjust the settings to improve your performance. As long as you know what the "safe" values are and what not to exceed, you can pretty much wing it and still come out with a solid memory overclock. I plan to write supplementary guides explaining what each timing does and which ones are typically more impactful on performance so stay tuned for those. I also plan to write a guide specifically for AMD's Ryzen processors as the process is significantly different and warrants a different thread.

Lastly, I am hoping to see what you guys can do. Nothing gets me more pumped for overclocking than someone to compete against and I think it would be fun to show off what we can do, especially if you've just recently picked this up. Would be a great way to track your improvement over time. Looking back at some of my old overclocks, it's definitely a significant difference now compared to then.

Here is an example of my first time overclocking DDR4 back in 2015:

Here is an example of me overclocking DDR4 now:

If you asked my friends and myself a few years back, we would have thought that sub-40ns latency on DDR4 was impossible for 24/7 stability but it's most definitely possible. Here's to hoping we all keep improving. Just don't improve too much, I'd like to remain the best at something on this forum...