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Zen 2 & RAM overclocking

Sagath

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So with some downtime I finally got around to using the DRAM calculator mentioned in other threads here to try and tweak my system.

3900x
Asus x570-E Gaming
F4-3200C16D-16GTZR (Hynix AFR dies)

1585780118601.png

I'm having a lot of difficulty, and reading on various forums it seems I really shouldn't be. Most people plug these numbers and off to the races. For the life of me, I cannot get the settings in the calculator (Fast or Safe) to post.

If I just use stock BIOS XMP @ 3333 (FCLK synced at 1666) the system is totally stable, and has been for months. However, the RAM tRC is SUPPOSED to be 56 according to mfgr spec sheet for XMP, but the XMP setting posts up at 78 (as seen above), and it absolutely will NOT post with anything close to 56.

I'm going to go back in the BIOS and basically change 1 timing at a time, but I'm almost 100% positive the tRC is the culprit for not posting if I change it.

To be clear; what I have changed from my known STOCK stable settings;
[email protected] (FCLK 1666 sync'd)
Voltage block are inputted
Misc Items are inputted
Termination are inputted
CAD_BUS are inputted

This is definitely a new way of OC'ing, and I havnt even tried to touch the CPU (after reading that the gains for effort are quite minimal) so I thought I would start here.

Any suggestions?
 
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lowfat

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First I'd set the max Vdimm you are comfortable with. For timings, I'd highly suggest changing one timing, reboot, change next. Change 2-3 then I'd run 5 minutes of MemTest86+. You'll see right away if something is way unstable. Rinse repeat. Then more memtest. Do 1/2 hr, drop voltage a bit. Rinse repeat until it fails. Then raise it 3-4 steps and I'd do at least 4 full runs, although I did 8 as I still had errors show up after 4 runs.
 

Sagath

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Yeah, I figured this might be a bit of 1-by-1.

I've got my RAM set to 1.39 for now, as I've heard that its fine for my kit. I'll start with the main timings, change them, and leave the tRC for now I guess, and see how it goes. Just bugs me its the furthest 'out' setting, and I cant seem to bring it 'in'.
 

Sagath

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This is where I'm at that is stable. I trial and erroed by doing changes in batches of 3 until post, revisit, rinse repeat...

1585786162808.png

Essentially this isolates the problem(s) down to tRC and tRFC.

Last change I tried was tRC to 56 (g.skill spec). It posted, but crashed on stress. Not sure how to proceed from here. Any suggestions?
 

lowfat

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Do you have Gear Down Mode enabled? You can try disabling it if so, it is generally hard to get it enabled. But if it were me, I'd keep it on over tightening tRC.
 

Sagath

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Its enabled.

I'm scoring 136 against a 'best result' of 118 as shown by the calculator right now. I'm gonna pull down the tRC & tRFC a couple points at a time and see if I can dial this in. I'm leaving about 10% performance on the table right now, according to this, that seems like a lot.
 

JD

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I'm not entirely sure where those "best" results come from though... even when my settings are identical to what it suggests, I still score worse.

As far as I can tell, your RAM is only 3200 but you're running it at 3333? Could be why you can't bring the tRC or tRFC down.

What voltages are you running? I've seen people running 1.45V+ on their RAM to get the frequency and timings stable.
 

Sagath

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1.39v And yeah, its 3200 for stock XMP. I'm running 3333 right now. Got the timings down to 'fast' minus tRC (at 60) and tRFC (at 520). I saw that some calculators out there will show the math between running slower speeds and tighter CL vs faster speeds and looser CL's. I'm not gonna go that far down the rabbit hole.

Right now, I'm at 129.5 vs 118 (best). I started at ~140, so there would appear to be (at least in benchmarks) a definitive difference, which I'm happy about. This feels easier to tweak than CPU mhz for overclocking. Which is kind of nice. CPU's are a lot of work to OC.
 

Valkyrie

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Super tight tRC doesn't help in most cases, but tightening tRFC does. Don't forget that tRC can be no less than tRAS + tRP, and that tRFC should be an (even) integer multiple of tRC. I put "even" in brackets because as I recall any integer multi (that is less and works) is better than a fractional multi, but I stand to be corrected. The tRFC is basically how long the bank is unavailable for access during refresh.

https://www.techpowerup.com/review/amd-ryzen-memory-tweaking-overclocking-guide/8.html


Playing with RAM timings is great fun and (possible) frustration if you push certain things too far....resulting in a corrupted OS,,,

Good luck!
 
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Sagath

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Super tight tRC doesn't help in most cases, but tightening tRFC does. Don't forget that tRC can be no less than tRAS + tRP, and that tRFC should be an (even) integer multiple of tRC. I put "even" in brackets because as I recall any integer multi (that is less and works) is better than a fractional multi, but I stand to be corrected. The tRFC is basically how long the bank is unavailable for access during refresh.

https://www.techpowerup.com/review/amd-ryzen-memory-tweaking-overclocking-guide/8.html


Playing with RAM timings is great fun and (possible) frustration if you push certain things too far....resulting in a corrupted OS,,,

Good luck!
Thanks for the help. I'm still stuck, as it doesn't seem any changes I make with tRC or tRFC will allow a POST. Auto defaults tRC to 78 and tRFC to 584, which doesnt add up math-wise with all the things you're saying and I'm reading, but will post. I also ran a longer mem test at these settings and got one error overnight. I'm tempted just to go back to XMP settings, up the mhz/fclk and call it a day. It works, anyways...
 
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