X99 DDR4 Memory Overclocking Guide


DDR4 Overclocking with Hynix MFR

So you want to overclock your fancy new DDR4 kits? Alright well here is some of my experience that can aid you in your journey and perhaps save you some time.

The RTL Game

This is the biggest factor of DDR4: RTL
Im no scientist but I do know that the tighter/lower your RTL value is, the more “free” performance or as the latest overclocking phrase (for when you dont have good hardware and you are bored) high efficency. Im not going to bore you with the science behind it, partly because I have no idea but here are the basics and some easy extra performance.

RTL is directly Connected to your tCL(Cas) tWCL and IOL Values.
The lower your tCL and tWCL the tighter your RTL value should be set by default.

For example:

Cas 16 and tWCL 16 will make RTL 61/61/61/61.
Cas 12 and tWCL 9 will make RTL 51/49/51/49.

Heres a chart with optimal RTL value with different tCL and tWCL values.
You can check these against your boards default and make changes accordingly.


IOL Values

This brings us to IOL Values, I like to think of them as the fine tuning portion of RTL tweaking. IOL values that we care about are listed below.

For example:

Cas 12 with tWCL 9 and IOL 8/8/8/8 makes RTL 51/49/51/49.
Cas 12 with tWCL 9 and IOL 6/8/6/8 makes RTL 49/49/49/49.

Lowering IOL values will help you to lower RTL and increase your performance.

Sometimes IMC and or quality of the memory will hold your performance back. If this is the case then you can loosen RTL by forcing a higher IOL such as 8/8/8/8.

What to Buy

So now that we know about RTLs we can hear some truth about what kits you should target to buy.
The answer is anything 3000 MHz C15 or higher is your best bet. But on the same thought, buying 3333 MHz C16 doesnt guarntee you a better kit!

For example:

G.Skill 3000 MHz C15 on XMP will set tCL 15 and tWCL 14 which in turn will give you RTLs of 57/57/57/57. G.Skill 3300 MHz, CL16, tWCL, 16 RTL will give you RTLs of 61/61/61/61 and G.Skill 3200 MHz, CL16, tWCL 15, RTLs of 59/59/59/59.
All of these are likely to give you similar performance within a second of eachother on SuperPi 32m.
So its my recommendation to buy 2 sets of 3000 MHz C15 instead of 1 set of 3300 MHz C16 for the same price etc.


The BIN Phase #1

DDR4 is tricky in this sense. More than ever is it important to find good quality IC’s.
This stems from the fact that at certain frequencies adding extra voltage is not going to help you but actually hurt your overclocking stability.
Its not like DDR3 MFR that will scale to 2.0+ volts on air. So first we must find sticks that run nicely at moderate voltage.
I have tried 4 different high bin G.Skill kits. And all of them have 1 sometimes 2 sticks that are way worse then the rest.

The BIN Phase #2

Okay so you bought you 2 kits of high binned DDR4 because you know there will be junk sticks mixed in. Now wat?
Now you bin, bin and bin. Maybe you are so smart you didn’t even read this guide and you jammed your expensive kit into your expensive board and now you are wondering why 4000 MHz CL8 is not working for you. Stahp! Slow down! Step 2 is a long step.
We are going to bin each stick one by one in slot B1 aka second physical slot from the socket on the IO side.
You can use whatever settings you like to bin as long as you dont change settings while binning.

Example: DDR4 binning by Splave

CL11 at 3000 MHz using 4 GHz CPU speed and 4 GHz Cache speed at a DIMM voltage of 1.65v.
Find the lowest voltage it will take to pass SuperPi 32m consistantly. Now you have found your best 4 sticks.
Don’t feel limited by my example. You can use 3200 MHz and C12 or anything you would like (there are some suggested timings at the bottom of this article).
We aren’t done yet. Now we are going to try each of our 4 binned sticks in each slot 1 at a time.
So start with A1 slot, find the lowest voltage for 32m. Then on the B1, D1, and then C1. You will end up with a scientific list of why you are putting each stick where they will fly the highest.
Pro tip: Slots in order from IO side to 24pin side go A1 B1 D1 C1. Dont get confused that they aren’t in alphabetical order on the boards left to right.
If you already know what you are doing and think this step is not necessary, gtfo and dont read my guide. Shamino labels his sticks for this reason nuff said?

Timings/Frequency Combinations.

So now that our memory is in its porperly proven correct slots, its time to max it out in quad channel.
The best frequency to timing ratio is 3200 Cas 12 followed by 3100 Cas 11.

Here is a standard tight Hynix 3200 Cas 12 timing set using 1.65-1.72 V:
12-13-15-14-1N-10-260-4-6-3-9-4-24-3-9 4-6-6-6-7-7-2-1-3-3-1-1-32767 49-49-49-49-6-8-6-8

Here is a standard tight Hynix 3100 Cas 11 timing set using 1.65-1.72 V:
11-13-15-14-1N-10-260-4-6-3-9-4-24-3-9 4-6-6-6-7-7-2-1-3-3-1-1-32767 47-47-47-47-6-8-6-8

An important thing to know is that memory training can be difficult with such tight timings.
So what we can do is keep it loose in the bios and for the training then tighten it down once we get into the OS using e.g. the AsRock Timming Configurator.
Keep in mind that tCL and tWCL will need to be set in the bios correctly as RTL and IOL’s cannot be changed in OS.

The key is to take the time to learn this over a week or two. It will make you a more well rounded overclocker and will help almost every benchmark you run from here on out! Don’t get frustrated by BD and BF bios codes, keep pushing and don’t give up.

Questions or suggetions? Let me know in the comments.

Splave – Overclocking.Guide


  • Hiwa

    Very nice and detailed guide Allen.

  • Awesome detailed guide

  • Jb

    Thanks for sharing! Great guide.

  • Sam

    Where can I get Hynix that does 1550 CL11 at 1.65V? 😀
    The best out of twelve 3000C15 sticks I’ve tried so far barely did 1500 CL11 at 1.72.

  • Splave

    Dancop and Fred have no issue here man 🙂

    I think you need to try some more sticks, I know I have 1 really bad one that was holding me back originally.

    • Sam

      Damn. I’m using 11-13-15-30 _ 16-320-6-7-6-10-8-32-6-10 _ 4-6-6-6-7-7-2-1-3-3-1-1-11440 for initial binning (purely for MHz/volt testing) and none of my 3000C15 sticks will even POST 1500MHz with these timings at 1.65V.

      Guess I’ll have to wait until Skylake to bin dual kits instead of quads, to prevent further wallet damage 😀

      • Sabishii Hito

        Don’t feel too bad, Sam. I have eight MFR sticks so far (LPX 2800C16, HyperX 2666C13) and none of them will POST at 3000 C11 1.65v either. I need at least 1.70v to boot to Windows and even 1.75v can’t pass 32M.

  • Hiwa

    One bad sticks hols me back from 12 I got 3 good. Will be interesting if I find one more them try ln2 difference between the kit I did 3100 c10 under ln2 with new once I have here is about 180 MHz on air.

  • Sabishii Hito

    Any reason why tREFI is set so high? Man DDR4 timings just don’t make any sense to me at this point, hate having to just copy settings. I have some Vengeance LPX 2800C16 Hynix, don’t think any of the sticks can do C11 stable though one at least booted to Windows. C12 works fine.

  • splave

    It’s high because it’s free performance for typing in 5 numbers. Higher trefi the better.

  • Sabishii Hito

    Any chance of a Samsung DDR4 guide? Seems a lot of kits that were Hynix are Samsung these days (I unwittingly ended up with two Samsung-based parts).

  • Wizerty

    Really nice guide, tks for sharing

  • nexxusty

    This was an awesome guide.

    I’d love to talk more with people about overlooking X99 RAM to its highest potential. I’m thinking HWBOT forums it’s going to be my new home. Anyone else have any input on this for me? 🙂

  • NilKilla

    Nice stuff! I’m glad I found this site!

  • Pingback: [DDR4 - Predators!] Kingston HyperX Predator 16GB DDR4-3000 CL15 Kit - www.hardwarezone.com.sg

  • Marcolecorse

    Very nice Guide

  • Here is a standard tight Hynix 3200 Cas 12 timing set using 1.65-1.72 V:
    12-13-15-14-1N-10-260-4-6-3-9-4-24-3-9 4-6-6-6-7-7-2-1-3-3-1-1-32767 49-49-49-49-6-8-6-8

    Here is a standard tight Hynix 3100 Cas 11 timing set using 1.65-1.72 V:
    11-13-15-14-1N-10-260-4-6-3-9-4-24-3-9 4-6-6-6-7-7-2-1-3-3-1-1-32767 47-47-47-47-6-8-6-8

    hi Splave, would you please match the number above with Asrock Timing Configurator? Since I cannot really match them in bios…. Thanks.

    And another question is, is there any subtiming related to the ROL and IOL? Because once I set them to like 49/49/49/49 @3200C12 I always failed when reboot the system. But I cannot change the RTL/ IOL value in OS with Timing Configurator.

    Looking forward to the feedback

    Thank you!~

  • nexxusty

    Hey guys, I have a Hynix MFR 16gb Quad Kit. Corsair Vengeance LPX 16gb 2666mhz ver 5.29.

    100% Hynix MFR IC’s. I’d really like some opinions on the best timing set to use for gaming?

    That is all I do on this system. I’m thinking latency would be key for a gaming system. I usually try to build a very low latency gaming system. Bandwidth is clearly not an issue on X99 for gaming. Or anything else for that matter.

    These 3200mhz Cas 12 @ 1.65v timingsets you guys have here, is 1.65v safe at all for 24/7 use or only SuperPI runs? I use 3200mhz Cas 15-15-15-35-1T @ 1.4v currently. I was told these IC’s don’t scale past 1.4v really at all.

    Can someone set me straight what ever the situation may be? I know there is a LOT of untweaked performance left in these IC’s. Reminds me of Micron D9 some years back. 🙂


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