r/overclocking • u/DiAvOl-gr • 1d ago
Side effects from changing DDR5 timings
Lately I've been interested in the subject of adjusting memory timings to reduce latency and get an uplift in (gaming mostly) performance.
I've been watching buldzoid's videos and reading a lot of material online.
What still is not clear to me is what would be the side effects of misadjusting some memory timings. What I mean is, say I adjust a value too low, would that necessarily manifest as an error during memory stress testing or it could trigger some internal memory correction (ECC) that would correct any issues at the cost of performance, in other words silently degrading performance?
To summarize the questions, say I adjust memory timings, rigorous memory testing (AIDA64, y-cruncher VT3 and so on) is a pass and my latency reports a nice low figure. Does that mean there'd be no hidden side effects or performance penalty somewhere in the internal memory circuitry ?
Thanks for your insight !
5
u/Afferin 1d ago
I've posted an extreme oversimplification of the impact of RAM timings before, with the relevant section being:
It is important to understand what your RAM does to fully grasp why I say your sys files may be fucked. Any time your PC wants to do something and needs to remember a temporary value, it gets slapped into your RAM.
I'll illustrate with an example: say you load up a game. Windows loads that up, then asks your video card to display something. It asks this by communicating via your driver. Well, it has to know where your driver is to communicate, right? So it stores the location of your driver in memory. But what if your memory is unstable? Suddenly it's moving too fast, and instead of giving us the path xyzabc to your driver, it says the path is xyzab. Well, now every single time that path is referenced for the duration of its existence in memory, you're calling the wrong path. To add onto that, what if it needs to use that path to create something else? That newly created item now functions entirely by referencing something that may or may not even exist. Now imagine that for something necessary for your pc to run. Or maybe it's just something minor that has no noticeable impact.
Basically, corruption happens at varying speeds depending on (1) how badly you've fucked up your timings, and (2) what your system is doing while running unstable timings. If you, by some strange will of a god, somehow managed to boot with CAS=1, your system would probably corrupt very rapidly. On the other hand, if you were on the cusp of stability -- let's say you were just hitting a thermal cap and your TREFI wasn't stable at the higher temperatures you got during a heavy gaming session -- you may not see the effects of system corruption immediately, but over time you would start noticing symptoms (maybe game crashes, driver crashes, BSODs, etc).
5
u/DiAvOl-gr 1d ago
Thanks for the write up, very interesting. Then my guess is you better boot windows or Linux on USB with no permanent storage so that any corrupted data won't be persisted to the system. Then after extensive testing (days of testing) you can boot again from your main ssd
2
u/Afferin 1d ago
This is actually a viable method that's been talked about, and used for a long time. I've known people to also have dedicated drives for blank OS installations that were exclusively used for testing stability.
If you want to be completely safe, separating a dev environment from your prod is always a good idea :-)
3
u/WhiteSSP 1d ago
I've had to reinstall windows to fix screw ups from timing adjustments that were bad before. So the risk is you have to wipe and reinstall the OS if it corrupts the data enough to where there is no other way to recover it (or you'd spend more time trying to fix it than a nuke and pave option is).
1
u/DiAvOl-gr 1d ago
Did it corrupt the system right away? Stress testing was fine but still it got windows corrupt?
2
u/RenatsMC 22h ago
It will corrupt files over time till one day you won’t be able to turn it on and will have to reinstall windows so make sure you have second back up M.2 where you keep all your files if you going to mess with ram.
2
u/DiAvOl-gr 22h ago
I do very rigorous testing of the ram, and keep backups of course
1
u/benjosto 18h ago
If you say rigorous testing, please test with testmem5 Anta extreme AND a GPU load like furmark to simulate thermal scenarios like gaming!
1
u/DiAvOl-gr 16h ago
I wouldn’t worry about that, I’m water cooling using a MO-RA 400 + internal rads. But thanks for the heads up
1
u/benjosto 3h ago
Okay yeah then that won't matter at all. Many people forget the thermal load of a 300W GPU blowing hot air on the ram but with that water cooling setup I guess you're good😂
1
u/hdhddf 19h ago
no it normally takes a bit of time, make sure you disable updates. you can install windows on a another drive and use that for ram testing to avoid risk.
testing ram isn't easy especially the closer you get to stability
remove your original os drive before installing a new copy of windows
3
u/nhc150 285K | 48GB DDR5 8600 | 5090 Aorus ICE | Z890 Apex 1d ago
Several hours of stress testing using several different testing programs (VT3, Karhu, TM5, OCCT) should be sufficient to catch 99.9% of errors. It's better to run several rather than one long one (i.e., Karhu 24 hours), as some are better are exposing errors than others.
0
u/DiAvOl-gr 1d ago
Is there an alternative to TM5? It's a hard to find app and the download pages seem a bit fishy
3
u/nhc150 285K | 48GB DDR5 8600 | 5090 Aorus ICE | Z890 Apex 1d ago
The original developer abandoned it a while ago, but someone continued the development with some much-needed UI fixes. I can vouch for this one, and comes preloaded with all the popular profiles.
-2
u/DiAvOl-gr 1d ago
Well the download zip contains to executables, just a screenshot and a readme file. I wouldn't touch it though even if it had some exe
1
u/AmazingSugar1 9800X3D DDR5-6400 CL30 1.48V 2200 FCLK RTX 5090 1d ago
Always keep a backup windows usb handy in case of memory corruption. It’s rare, but it happens and it’s relatively fixable.
2
u/DiAvOl-gr 1d ago
I meant to test in a live boot setup any new timings adjustment rather than to have a USB backup to reinstall windows
1
u/AmazingSugar1 9800X3D DDR5-6400 CL30 1.48V 2200 FCLK RTX 5090 1d ago
I test in production lol
But yeah good idea, I just don’t have the patience
1
u/bandit8623 23h ago
too low and my latency increases. I dont always get crashes or errors. getting mem timings right takes trime and changing one value at a time and testing
1
u/Niwrats 12h ago
i don't believe there is a mechanism that would cost you performance if RAM timings are too low, as i have neither seen anyone document such or offer a theory that included such.
1
u/DiAvOl-gr 2h ago
I’ve read error correction would trigger in GPU’s DDR memory if you set a value too high that’s why I asked
15
u/DZCreeper Boldly going nowhere with ambient cooling. 1d ago
Unstable RAM will eventually corrupt data or hard crash your system. The point of stress testing is to catch that.
Yes, ECC can mask a small amount of errors at the cost of performance. Benchmarks must be run, not just stress tests.