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Discussion Starter · #1 ·
Exciting day... I had both of my patriot viper ram pairs arrive at the same time from two different sources :cool:

Board is a B550 pro ac
My dimms are rated for cl19 4400. But they don't even post at xmp1 (4266) Not that I expected them to... on am4, anyhow.
I'm trying to learn the intricacies of the timings, but I can see it will take some time.
So far, I have had it at 4000 cl15 and 2000 fclk with no issues, but just like with my old kit, the performance I see is negligible versus 3800/1900


So, that is where I have it.

Untitled.png

Need to so some stress testing, and then try and dial things in. But am glad to at least be able to ditch my ram cooling fans now.

DSCF5899_edited_edited.jpg
 

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2 DIMM kits never boot xmp 1 in 4 DIMM configuration. Patriots have an XMP 2 mode which should boot. I also have 2 kits of Patriots and the 2 DIMM performance is very close to the 4 DIMM performance, within 133 mhz.
 

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Discussion Starter · #3 ·
For whatever reason, the newest AMD processors get a nice performance bump using 4 vs 2 dimms, even on only dual channel.

Both XMPs fail to post, but most zen 3 processors don't like running much past 4000 mhz anyhow.... if even than much. My old CJR kit ran 3933 just fine, but you can tell that the system is more consistent at a bit lower memory speed. That and I have to run a lot of vsoc voltage for higher speeds, so I'd just rather not.
 

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Good to know. I just got a 2 DIMM motherboard and I’ll be selling 2 very capable Patriot kits soon. They should serve a Ryzen owner very well
 
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Did this help solve your stability issues (SoC auto voltage) etc? CL15 / 4Ghz is pretty nice :)

Yes, diminishing returns are a thing. Eurogamer did a nice write up on RAM latency / speed and it's real impact to gaming.

 

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Discussion Starter · #6 · (Edited)
I have soc set to 1.21 currently. I was running it most stable at 1.14 at these speeds on my cjr kit (cl16/3800) but with much looser timings. New kit won't post at that soc voltage/speed.

My stability prior was caused by pbo altering my cpu core voltage too much over a period of a couple days. And also by my old ram kit if it ever got much hotter than 35C.

Currently upped voltage to 1.52 on the dimms, and temps hold steady at 40C with no stability issues. And without my cooling fans
 

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That 35c issue made no sense. Glad you made the swap for a kit that doesn't self combust :)

I'd just be careful with running 1.52v, daily. Good luck with the tunning :)
 

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Discussion Starter · #9 ·
The temp issue was weird, and I would have never solved it if I hadn't bought a ram cooler on a whim. It was consistent, though. About 10 minutes into a bench every time. I thought at first I botched the waterblock install on my gpu becuase it was triggering nvidia driver crash (some others, but that a lot) but I couldn't find any Hotspots on my gpu using IR. I think at some point I started measuring my ram temps without the cooler and saw the pattern (after adding the cooler fixed the issue)

Yeah, I'm not comfortable going any higher than 1.52. I'm going to dial it back some of I can. But I was getting some instability at 1.5 during testing. I did adjust some other timings, so will go back and check 1.5 again
 

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If we're getting that granular, it's best to check the specific kit and manufacturer specifications. Yes, manufacturing changes so it's worth noting.

Thanks for sharing :)
 

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For whatever reason, the newest AMD processors get a nice performance bump using 4 vs 2 dimms, even on only dual channel.
Rank interleaving. Doesn't necessarily require two DIMMs per channel, but does require at least two ranks per channel. Your DIMMs are single rank though, so you need to fill all four slots to have dual-channel with two ranks per channel.

Intel benefits too.

The temp issue was weird, and I would have never solved it if I hadn't bought a ram cooler on a whim. It was consistent, though.
B-die at 1.5v+ can get hot, even single sided. I would use TestMem5 and a GPU test simultaneously with fans turned down to get worst case memory temps.

Yeah, I'm not comfortable going any higher than 1.52. I'm going to dial it back some of I can. But I was getting some instability at 1.5 during testing. I did adjust some other timings, so will go back and check 1.5 again
I would try reducing that RttPark if possible. RZQ/1 (240ohm) is a lot of impedance.
 

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Discussion Starter · #14 ·
Thanks for the tips 🙂 given that the xmp profiles were basically useless I made some small tweaks to the default 2133 timing. And it runs very close to the same timings for 3800 and 4000

As for temps, I've run it for extended periods and only seen 40C without the cooler installed. (using IR temp sensor on hottest portion) My old hynix kit basically required that it be under 35C to remain stable

I'll take a look at rttpark. Should I modify rttwr? Or procodt? I've tried lowering both before because they did seem high, but
Maybe I lowered too much. System didn't like it (set rttpark to rzq5, and procodt to 43.6)
 

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Proc ODT of 60 ohm is very high for Zen 3. Don't run that long term if you can avoid it, certainly not at 1.5 vDIMM. Try to stay under 48. Though realistically, once you get settings dialed in 40ohm or less should work.

Try RttPark of RZQ/2 or /3. RttNom of /6. RttWr of /3 should be fine, but some quad single-rank configs like it disabled.

Note that termination values are stronger/hotter the higher they are, but that the drive strengths work the opposite way. Lower resistance values are stronger drives. I normally start at 60/30/30/30 and adjust down (stronger) from there.

Also there are some timings that are needlessly tight, especially for GDM. You can probably set the following:

tRDRDSCL = 4
tWRWRSCL = 4

tRDRDSD = 4 or 5
tRDRDDD = 4 or 5

tWRWRSD = 6 or 7
tWRWRDD = 6 or 7

...and not lose any performance at all. Might even gain a little.

tWTR_S and tWTR_L might be a touch on the tight side as well. Loosening them to 4 and 10-12 might give you a bit more room to tweak or reduce voltage/termination impedance, without hurting performance much...though you won't gain any.

tWRRD might need to be loosened to 2 or 4. This will hurt performance ever so slightly, but B-die often doesn't like it at 1 and it usually costs more than it's worth to run it.

Conversely, you can probably tighten tRAS, tFAW, and tRFC. You can definitely tighten tRCDWR, probably down to 8 or 10.

As far as voltages go, running memory termination voltage slightly less than half of vDIMM can occasionally help.

Your vSoC, CLDO VDDP, and CLDO VDDG CCD are probably slightly too high. CLDO VDDG IOD might be a touch low, however.
 
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Discussion Starter · #16 ·
So, I've got some interesting results. I wasn't able to get the voltage down lower. Nor resistance. Maybe due to my 2 kits being from different revisions? I don't honestly know. One kit shows a mfg date of the year 2000 lol. The other 2020.

One thing to note... It seemed a gained a TON of stability by accidentally setting vsoc to auto. Although my settings were at times identical....?

ZenTimings_Screenshot.png
 
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