DDR5 overclocking (nightmare)

[Admin]

While CPU and GPU overclocking is relatively straightforward DDR5 overcloking can be an utter nightmare.

As you increase the DRAM frequency you will become increasingly likely to run into some stability issue. These stability issues can be very difficult to find in stability testing so you might think you have gotten your overclock stable only to then later down the line find some stability issue after doing further changes.

Stability issues can be due to the ram dies themselves becoming unstable but it can also be due to the memory controller that is integrated on the CPU or bad signal integrity between the CPU and the RAM. The imc will become a much bigger problem if you run more than 48 GiB of DDR5.

Since the memory controller sits on the CPU heat from the CPU cores can interfer with the imc making it less stable.

 

[Admin]

1. Maximizing the DRAM frequency
Your first priority (after inclreasing tREFI to maybe 65528) is increasing the DRAM frequency as high as you can without it becoming unstable.

Increasing the DRAM frequency will also reduce the latency if you keep using the settings that came with the XMP profile. Eventually however some of these timings will become too tight as you push up the frequency higher. The issue then is that you do not actually know which timings (if any) that needs to be loosened if you nbaoticed instability so you might end up having to loosen up all in order to later tighten them up again until you find the culprits.

As you increase the frequency the minimum stable voltages will increase. Unfortunately more voltage also mean more heat which itself can cause stability issues. Too high voltage can also be outright dangerous for components and this remains the case even if your temperatures are all safe. Higher voltage can also result in more signal distortion, especially on cheap motherboards.

The ICs just have a point where the voltage doesn't scale anymore or the scaling even turns negative. It doesn't even have to be temperature related. I have an old B-die kit that runs great with 1.500V but anything more than that and it's goodbye stability. I've literally tested the sticks at under 10C temps and that didn't change anything.

higher voltage can obviously result in less stability, since overvolting is a thing, as it can ruin signal integrity and overall the signal-to-noise ratio (SNR).

It does not always depend on the motherboard, but rather on the CPU sample too, that is also why different CPUs behave differently.

I found the following voltages to result in stability at 6461 MT/s and 64 GiB of ram (dual rank) on the cheapest msi z790 motherboard.

CPU VDDQ: 1.26
CPU SA: 1.2
CPU VDD2: 1.39
DRAM voltage: 1.4
DRAM VDDQ voltage: 1.4

Since the g.skill ram has a terrible heat-spreader i ended up using a fan to keep the ram cool. Unfortunate with raptor lake it's hard to max out that memory in terms of frequency due to the sub-par imc, you end up having to run the memory in "gear2" which is slower than gear1 to get it stable and even then even reaching 6400 MT/s stable will be a challenge when you use more than 48 GiB. In addition the motherboard might also limit my overclocking headroom. Just getting it fully stable at 6400 difficult likely due me not having a proper CPU cooler contributing to higher IMC temperatures.

With single rank ram you will start running into imc issues at around 7200 and of course it becomes progressively harder to get it fully stable past that (at least in gear 2).

 

[Admin]

2. Stability testing
There isn't any single program you can rely on for reliable stability testing, instead you end up having to use multiple programs to verify that your ram overclock is indeed stable.

http://www.numberworld.org/y-cruncher/

There are a lot of different ways in which you can use y-cruncher. The VST test might be the most useful when it comes to stressing the memory controller but that test alone will not detect all errors. By default each sub-test will run for just 2 minutes which might not be enough to verify that there isn't any instability due to continues stressing in the same way. It seems like changing the time each test runs to 600 seconds make it harder for unstable overclocks to pass.

These tests will in rare occation fail to find error when you have some memory stability so you might want to run more tests if 100% stability is the goal.

HCI memtest aka memtest pro

Prime95 using the "largest FFT" or "blend" setting.

Linpack Extreme

https://github.com/stressapptest/stressapptest

It's made specifically for linux but you can use it on windows via WSL. Use the following command to run it and test 32GiB of ram:

stressapptest -s 36000 -M 32768 -m 32 -W

Unfortunately that alone is not enough to find all potential instabilities despite taking 10 hours. One issue is that it relies solely on copy operations and might then miss stability issue if your read and write performance doesn't match (bottlenecking the stresstest) it also doesn't seem to stress the memory controller as hard as some y-cruncher tests. Still it's very good at catching errors and a good option if you use linux, it can sometimes quickly find instability that y-crunches missed despite running for hours.

These tests are good at booth loading the CPU and RAM at the same time which is particularly useful when you are imc limited.

Testmen5 will not stress the CPU much which is bad if you want to test if the imc is stable at the frequency it's running at under max cpu heat generation.

 

[Admin]

Tweaking timings
There are a lot of different timings you can configure. These can have a massive impact on performance but if just one of them is too tight you end up with an unstable system.

By default tREFI is often set way to low resulting in a performance loss of around 8%. Higher tREFI is actually better in terms of speed (unlike almost all other timings where lower is faster or same speed).

You can try setting tREFI to 65528 or 130560 and get 6% to 10% performance uplift. This is arguably the first thing you should do when it comes to ram overclocking.

It's recommended that you do save a bios profile each time you change your timings. If you then find a stability issue you just go back one step at a time until the stability issue disappears. The reason for this is that properly stability-testing DDR5 is very arduous, especially when you have more than 32 GiB. It's probably faster not to properly test for instabilities and just move on since you discover it later down the line eventually anyway.

 

[Admin]

Tertiary timings are very important
Having any of these be too high can have a massive impact on performance.

tRDRDDG higher than 8 reduce read bandwidth by around 15%

TWRWRDG higher than 8 will reduce write bandwidth by around 15%

Try also setting tRDRDSG and tWRWRSG to 16 or less

Try setting tWRRDSG to 64 or less.

sg = same group
dg = different group
dd = different die (same channel, different die)
dr = different rank

The dd timing will only be used if you have 4 ram dimms.
The dr timing will only be used if you have dual rank memory (such as 2x32 GiB).

tWRWRSG at 14 results in worse performance than setting it at 16, that can result in changing it from 14 to 16 resulting in instability due to the higher performance unmasking some other instability.

 

[Admin]

The importance of a good motherboard
Some motherboard will be able to clock the ram much higher than others. The exact mechanisms for this is a bit unclear.

X61 reported that replacing msi pro z790-p with asus maxiumux z790 apex allowed ram overclocking to 7200 MT/s istead of struggeling to reach stability at 6600 MT/s with 2x32 GiB (dual rank) DDR5 (A-die).

A sign that your motherboard is bad is that you get your ram stable with low CPU VDDQ and CPU SA voltage but then cannot go higher even if you raise these.

One thing you can test is changing which slots you install the ram in. If it's a good motherboard changing to the other 2 slots shouldn't negatively affect how high you can overclock but some motherboard vendors cheap out on 2 of the slots making them worse than useless.

The old asus prime z690-A is limited to just 6200 in single rank operation.

You might think that the msi z690 unify-x would be good since it has just 2 ram slots but it actually isn't that great

M-die Power!!!! This is how tight I could get this kit, very impressed. I literally maxed out the trefi! 7800 was a no go. tried up to 1.7v, no dice. This is getting the same latency as my Gskill A-die at 8200 C36. I think I am returning both my A-die kits and keeping my M-die for a little longer.

Z790 Apex is a BEAST of a board... on my Z690 Unify-x with the EXACT same processor, The best I could get stable on this kit was 7000 C34, now I am doing 7600 C32, lol. Btw, for anyone that is wondering, my MC SP is between 80-82 whenever I check it.

overclock.net/threads/official-intel-ddr5-oc-and-24-7-daily-memory-stability-thread.1794772/page-545#post-29093503

 

[Admin]

What to look for when buying DDR5
With raptor lake you want to stick to 2 ram sticks. If you want 64 GiB you should buy 2 sticks of 32 GiB each rather than 4 sticks with 16 GiB each.

2x32 will be dual rank which is much harder on the memory controller but it also performs better than single rank at the same frequency. It's actually not clear what the best option is in terms of getting the best performance besides the fact that you get twice the capacity when going with 64 GiB which itself is very useful.

lately 2x24 GiB kits have emerged which does seem to overclock as well as 2x16 kits since they are single rank, that might be a good option if you want high ram bandwidth (over 120 GiB/s and also more than 32GiB of memory).

It's also not clear that hynix A-die would be better than hynix M-die. It seems like A-die is worse in terms of timings which is a significant disadvantage and often you cannot even take advantage of the higher frequency potential offered by A-die due to motherboard/IMC limitations.

Samsung memory tends to have the first 3 primary timings be the same such as 6000CL36, 36, 36

A-die and M-die tends to have lower cas latency while the tRCD is significantly higher such as 6000CL32, 38, 38, 38 and 6000CL30, 40, 40, 40

Samsung DDR5 does seem pretty good in terms of latency but it overclocks worse than M-die, overall M-die is a bit better and you don't save much/any money by going for the overall inferior samsung DDR5.

So given that there isn't any clear advantage for any type of memory you might just grab the cheapest 6000+ MT/s kit you can find since it's probably going to be good regardless besides the difference in cooling and the minor differences in terms of silicon quality. Maybe just skip samsung so look for 6000CL30 or better.

 

[Admin]

BLCK overclocking
The BLCK will not only affect the ram clock. It will also make your CPU faster and more efficient due to less voltage being applied relative to the frequency (unless you use static overclock where the voltage is fixed). This is a very good thing to do if possible.

You can find out the max stable BLCK frequency for the CPU simply by lowering the DRAM multiplyer to a lower value to make sure any error you see is from the CPU and not due to you pushing the ram/imc too hard.

BLCK overclocking will sometimes produce very high aida64 read/write/copy figures due to a bug in the software. The actual perormance increase is no more than linear.

BLCK overclocking is very useful if you want to have a very stable overclock. You can simply tune it for maybe 102 BLCK and then when it seems to be fully stable make a second bios profile with the BLCK reduced slightly (such as 101.6), otherwise you might have a ram error occur once every 7 days or something like that.

 

[Admin]

Memory training
It has been difficult to find any decent information regarding what memory overclocking actually does in the case of DDR5 memory but i did find this explanation for DDR4, should be similar with DDR5:

https://www.systemverilog.io/ddr4-initialization-and-calibration

I got the impression that changing the settings in bios to "long training" made the ram more stable but i haven't properly verified this yet. Still this is something you can play around with if you struggle to get your ram stable with acceptable performance.

I have heard that rebooting can make your memory unstable due to it being trained even if you don't actually change anything in bios (due to the memory being trained again in the next boot resulting in the memory working slightly differently) but i haven't verified that myself yet.

 

[Admin]

Memory stability table at 6461 MT/s 2x32 A-die
I got what seemed like a stable 6461 overclock earlier but it later i discovered stability issues when i tested with higher room temperature. With a lot of effort i was eventually able to get an overclock that passed 23 hours of stresstesting.

DRAM VDD: 1.40
DRAM VDDQ: 1.40
CPU VDD2: 1.38
CPU VDDQ: 1.26
CPU SA: 1.2
BLCK: 101.2

SA PLL SFR voltage: 0.990
MC PLL SFR voltage: 1.02
memory fast boot: slow training

enhanced interleave: enabled
power down mode: disabled

This was done using msi pro z790-p (not recommended) using bios version A40 (A50 was worse).

          stable  unstable      testing
tCL       30      29(SAT)
tRCD      38      36         
tRCDw     37      36
rRP       32      30           
tRAS      32      24         
tRFC2     496                 

tRFCPB    432     372?
tREFI     65528             
tWR       60
tWR_MR    60
tWTR      8       6(SAT)
tWTR_L    12
tRRD      8       6
tRRD_L    10                 
tRTP      12                 
tRTP_MR   12
tFAW      32
tCWL      28      12??
tCKE      8
tCCD      8
tCCD_L    12
tCCD_L_MR 12

tRDRDSG   16
tRDRDDG   8
tRDRDDR   12

tWRWRSG   16      12? (HNT)
tWRWRDG   8
tWRWRDR   16      14

tRDWRDG   20
tRDWRDG   20
tRDWRDR   20

tWRRDSG   64
tWRRDDG   54
tWRRDDR   14      16??

tWPRE     2
tRORE     2
tWRPRE    48      46?
tRDPRE    16
tPPD      2
tXP       8       4? (HNT)
tXPDLL    16      4? (SAT)
tPRPDEN   2
tRDPDEN   6
tWRPDEN   6
tCDDED    16
tAONPD    0
tREFIx9   255
tXSDLL    64
tCQOPER   0
tMOD      48      42? (SAT)
tZQCS     84      64? (SAT)
tZQCAL    460     420? (SAT)
tXSR      256     42(SAT)
tREFSBRD  92      60(SAT)
tCSH      42      28? (SAT)
tCSL      6
tCA2CS    8
tCKCKEH   11
tCSCKEH   7
tRFM      280     256(HNT)
OREFRI    64

RTL initA 66
RTL initB 65
CHA/D1/R0 62
CHA/D1/R1 62
CHB/D1/R0 63
CHB/D1/R0 63

https://www.youtube.com/watch?v=ba55hKLlfDw

SenseAmp Offset Training: disabled
Early DIMM DFE training: enabled
DIMM RON training: enabled
DIMM ODT training: enabled
Write drive stength/equalization 2D: enabled
read ODT training: enabled
Read Vref Decap training: enabled
VDDQ Training: enabled
Round Trip Latency: enabled
Turn Around Timing Training: disabled

Earlier i did get what seemed like a stable memory overclock but later i discovered CPU instabilities and later i discovered memory stability issues even after i fixed those.

https://www.youtube.com/watch?v=mzELev8nUds

The reason why i initially used 65280 for tREFI is because tREFI9x cannot be set higher than 255 in bios so it's slightly better if 262120 is evenly divisible by tREFI. I later found out that you can push it as high as 65528 due to the actual value of tREFIx9 being one higher than the value in the bios (there was something else causing 65535 to be slightly higher than ideal).

SAT=stressapptest

This was tested with stressapptest since y-crunches failed to find stability issue with the following overclock (SAT later found instability after less than an hour):

https://www.youtube.com/watch?v=T9-UEM3PplM

At 6436 MT/s i got the following table earlier.

           unstable  stable
tCL        28        30
tRCD       36        38
tRCDw      36        37
tRP                  36
tRAS                 36
tRFC       435

tRDRDSG    14        16

tRDWRSG    18
tRDWRDG    18
tRDWRDR    18

https://www.youtube.com/watch?v=_6dk3zI3_74

While this was likely stable timings were pretty lose and i later had trouble getting it stable with tighter timings (until the recent stable 6461 MT/s overclock).

 

[Admin]

Memory stability table at 6220 MT/s 2x32 M-die
These timings were posted by zero989 and i do not know how hard these have been tested for stability.

 

[Admin]

Framechasers: you need to find the voltage sweetspot for your CPU
Like me he found that there will be windows of stability for the memory controller voltages that shrink as you go up in frequency and that this varies between CPUs so it might not be stable if you copy voltages from someone else even if he/she has the exact same models of everything.

He also found out that applying the XMP profile might not even be stable at higher frequencies (such as 8000 MT/s) which isn't exactly surprising either.

Note that he isn't actually particularly great when it comes to overclocking, he is mostly good for entertainment.

 

[Admin]

Settings for 7200 MT/s dual rank on the asus z790 apex
This was provided by the know banned overclock.net user X61. It did pass a moderetely hard stability test at least (he also DMd me screenshot of passing y-cruncher VST for over an hour).

The timings themselves are actually pretty bad. It's likely that he has optimized these further since getting banned, it's just that i personally have not had contact with him.

 

[Admin]

Settings for 7000 MT/s dual rank 2x32
This was tested lightly by DunkZone and no stability issue was found

They found 1.25 to be a good memory controller (CPU VDDQ) voltage which is in line with my findings.

 

[Admin]

Teamgroup T-Create 6400 (64Gb) DualRanks @ 6800-32
This overclock was achieved by pakhtunov and was subjected to heavy stability testing.

Unify-X A.91U1

DIMMA/B DRAM VDD=1.46 / DRAM VDDQ=1.4
CPU SA=1.2 / CPU VDDQ TX=1.32 / CPU VDD2=1.4
VPP=1.8 / CPU AUX=1.8

 

[Admin]

7800 MT/s stable with eVGA Z790 dark
Yet another example of having to lower the memory controller voltage to get it stable at higher frequencies, he tried 1.35 first and it just never worked so he had to lower it to 1.3

CPU VDDQ: 1.3
CPU VDD2: 1.6
CPU SA: 1.25
DRAM voltage: 1.58
DRAM VDDQ: 1.45

 

[Admin]

Buildzoid gave up on 8000MT/s
He got it very close to fully stable but just never the full way. This was with single rank 2x16 memory and many compinations of motherboard, CPU, ram. He didn't try the x790 apex though.

He did claim that how you mount the CPU can affect memory stability.

 

[Admin]

Hardware unboxed confirmed: XMP profiles are trash
We also see that dual rank DDR5 at 5600 was able to beat single rank at 6000 when using the XMP profiles which wasn't exactly surprising.

Maybe the biggest issue with XMP profiles is low tREFI value costing around 8% in bandwidth. It's very easy to change that to 65280 (or 130560) to get around 8% in free performance in minutes (takes hours to properly test for stability though).

 

[Admin]

Star-citizen benchmark: you want 8000 MT/s
This agained confirmed the importance of manual tuning.

https://www.youtube.com/watch?v=CITlrdWsaWE

 

[Admin]

The pakhtunov ddr5 overclooding guide
He did discover some tips for better ddr5 overclocking

He like me found that you couldn't manually change RTL timings on msi motherboards since that will prevent you from even booting. He did suggest changing "latency timings settings mode" to "dynamic" which i will try later to get 6600+ stable.

SenseAmp Offset Training: DISABLED
DIMM ODT Training: ENABLED
DIMM DFE Training: ENABLED
Write Drive Strength/Equalization 2D: ENABLED
VDDQ Training: ENABLED
Round Trip Latency: ENABLED
Turn Around Timing Training: DISABLED

Example of advice i disagree with is setting tREFI at auto at first, raising tREFI to 65628 is one of the first things you should do when overclocking ddr5, having it lower might mask some instabilities but that will just result in it taking longer to stress-test your system.

I did see that he did the same mistake of me in assuming that the highest possible tREFI without incurring performance penalty from tREFIx9 times 1028 not being nicely divided (with as small remainder as possible) by it would be 65280, i later found out that you can push it as high as 65528.

Copying overclocking settings others used will work in some cases but very often it just will not work. Copying settings from others can however save you a lot time while also providing a lot better performance than merely applying the XMP profile (due to how bad XMP profiles are). Often the XMP profile isn't even stable due to bad motherboard/CPU.

 

[Admin]

6933 MT/s stable 2x32
This overclock was provided by affxct

It wasn't subjected to rigorous stability testing but it should be stable enough for gaming at least.

https://1drv.ms/f/s!At1W2WsgGjF1xSO6fhoepH1ydoGq

 

[Admin]

2x32 GiB stable at 7400 with Z690 dark kingpin
It was at least decently stable. Tested for at least 3 hours. This overclock was provided by Ivan One

 

[Admin]

4x16 GiB stable at 7000MT/s with evga z790 classified.
This is the highest 4x16 overclock i have seen so far. Like many others he found that having too high memory controller voltage will make your overclock unstable (sweetspot in his case was 1.26 to 1.28 for CPU VDDQ)

CPU VDDQ: 1.26
CPU VDD2: 1.476
DRAM VDDQ: 1.45
DRAM VDD: 1.45
DRAM VPP: 1.95

 

[Admin]

Your overclock is never 100% stable
If you run a stresstest long enough you will eventually find an error. It¨s merely a matter of frequency of these errors.

Fundamentally physics isn't deterministic so you can never actually get a 100% deterministic computer. There is also the issue of radiation (icnluding cosmic rays) and this will be a bigger problem when you do not have full ECC memory.

Still if you find an error after say 20 hours of stresstesting that is still a cause for concern since there might be some scenario where errors will show up a lot more often than the rest you ran.

 

[Admin]

8400 MT/s stable
It was tested in y-cruncher for 91 minutes and testmen5 for 72 minutes with 0 hardware errors detected.

overclock.net/threads/official-intel-ddr5-oc-and-24-7-daily-memory-stability-thread.1794772/page-763#post-29175790

 

[Admin]

2x32 GiB stable at 6132 MT/s with tight timings
Loukiz had a bad motherboard/imc preventing him from even getting 6200 MT/s stable, he was howevere able to push the cas latency down all the way to 26 at 6132 MT/s which is very interesting.

dram VDD: 1.545v
dram VDDQ: 1.53v
VDDQ TX: 1.3v
CPU SA: 1.2v
VDD2/VDD_CPU: 1.376v

 

[Admin]

8200 MT/s stable (2x16 GiB)
This was subjected to lengthy stability testing with 0 hardware errors found

MickJones archieved this and wrote:

Hey guys - the 9901 Apex bios seems to be the magic bullet for my board. I was having trouble stabilizing 8200 before, but did so easily with this bios. I also tried the newest bios and it was not as good.

 

[Admin]

2x24 GiB at 8600 MT/s
This was provided by SoldierRBT and passed 22 minutes of y-cruncher VST

This illustrates that 2x24 GiB will overclock just fine. basically the same performance as 2x16 while providing 50% more capacity.

 

[Admin]

6400 CR1 with 7800X3D
This is an interesting overclock provided by u/WalrusOne8452

The read bandwidth is pretty bad, might be due to the CPU rather than ram settings.

 

[Admin]

2x16 GiB decently stable at 6200 MT/s 7700x
This interesting overclock was achieved by chewonthis and passed the y-cruncher FFT test

It's unclear if it would also pass other y-cruncher tests.

 

[Admin]

128GiB stable at 5600 with 7950x3d
The following overclocks were provided by Deveye and passed 7 hours of y-cruncher mixed

 

[Admin]

AMD now support higher DDR5 speeds
Their gear2 mode used to be broken but now it actually works. Of course there is a latency penalty going from gear1 to gear2 but overall performance might still improve.

A lot easier to get stable than 8000MT/s with raptor lake.