Prime95 fails due to memory

Joined
Sep 12, 2020
Messages
1
Hi Everyone, i've a problem with my newest ryzen 3900x build. The build fails the small fft test with Prime95 if i set the ram at 3600 or up, no matter the voltage, i tried also to 1.40v but no luck. The problem is that the ram supposedly should ran at 4000mhz, 16x2 Crucial Ballistix Max RGB 4000mhz 19-18-18-18

I tried different things increasing voltage, disabling XMP, changing timings, the only thing that work is lowering the frequency to a maximum of 3400: this way the prime95 pass for more that 1h. I was able to exclude a CPU problem (well i think i can exclude) because at 2667mhz lowest frequency, the CPU pass the prime95 for more than an hour, also undervolted to 1.20v. I also tried with different memories (3000mhz Dominator Platinum at 3200 15-16-16-16) at 3200 and the test is passed for more than 1h with the cpu in downvolt too.

Cinebench 20 runs with no problems at every clock speed, also multiple times.

My parts list is the following

Ryzen 3900x
Mobo Gigabyte Aorus X570 I pro wifi
Crucial Ballistix Max RGB 4000mhz
cpu Cooler Mugen5 tuf rgb
Case ITX InWin A1

I read somewhere else that i could try using Vcore offset +100 mV, or in another discussion, where the problem was related to the memory, switch VDDCR SOC Voltage to offset mode but don't know if this is the case, and plus i don't know where i can find it in the Gigabyte BIOS ...(not very familiar with it, as i'm a first time gigabyte user). Someone told me to simply don't care about prime95, or to change the infinity fabric to 1600 and the memory frequency to 1800, but in this case while the amd master stress test works, prime95

Can someone please help me ? Really really upset i can't use my new build safely
 

Aegir

Limp Gawd
Joined
Apr 15, 2020
Messages
415
I'm using that same Ballistix Max RAM in one of my systems, but I don't know much about how to deal with your issue.
I bought Ballistix Max for memory stability reasons. I bought RAM rated for those ultra-high speeds, but run it at 3600 and CL18 speeds.

I keep my FLCK tied with my RAM clock, at 1800 MHz. I'll try running Prime95 under my current settings and tell you what I get.

~~~
Actually, I'll run Prime95 after I reapply some thermal paste. Whew. Getting toasty.
 
Last edited:

kirbyrj

Fully [H]
Joined
Feb 1, 2005
Messages
26,823
I would bump the SOC voltage up slightly and make sure that the Infinity Fabric is 1:1 with the memory. I'd probably start by setting the XMP timings and then manually dropping the RAM speed to 3600Mhz. Then if you pass Prime95, tighten the timings or bump the speed.

Also, does your memory pass memtest86? I would work on getting the memory stable first, and then start with Prime95.
 

Ready4Dis

2[H]4U
Joined
Nov 4, 2015
Messages
2,367
Yeah, bump up SOC voltage slightly. Also, as mentioned by Aegir, it's possible to run it slower with tighter timings and end up with better overall performance, so don't just look at the highest MHz and assume that is the best. Keeping 1:1 with infinity fabric helps out, as does tighter timings in general.

This is just a high level example:
Ram TypeEffective ClockRamClock Cycle TimeCASLatencyBandwidth (MB/s)GB/s
DDR4
4000​
DDR4-4000
0.50​
19​
9.50​
32000​
32​
DDR4
3600​
DDR4-3600
0.56​
18​
10.00​
28800​
28.8​
DDR4
3600​
DDR4-3600
0.56​
17​
9.44​
28800​
28.8​

As you can see, DDR 3600 @ CL17 would give you better latency than running at 4000. Also having IF 1:1 will give better performance as well. For straight up memory bandwidth you do lose a little bit, but it is very dependant on your work load. For gaming and stuff, < latency is more important. For some other things (video editing for example) bandwidth might be more important.
 

chameleoneel

2[H]4U
Joined
Aug 15, 2005
Messages
3,422
Hi Everyone, i've a problem with my newest ryzen 3900x build. The build fails the small fft test with Prime95 if i set the ram at 3600 or up, no matter the voltage, i tried also to 1.40v but no luck. The problem is that the ram supposedly should ran at 4000mhz, 16x2 Crucial Ballistix Max RGB 4000mhz 19-18-18-18

I tried different things increasing voltage, disabling XMP, changing timings, the only thing that work is lowering the frequency to a maximum of 3400: this way the prime95 pass for more that 1h. I was able to exclude a CPU problem (well i think i can exclude) because at 2667mhz lowest frequency, the CPU pass the prime95 for more than an hour, also undervolted to 1.20v. I also tried with different memories (3000mhz Dominator Platinum at 3200 15-16-16-16) at 3200 and the test is passed for more than 1h with the cpu in downvolt too.

Cinebench 20 runs with no problems at every clock speed, also multiple times.

My parts list is the following

Ryzen 3900x
Mobo Gigabyte Aorus X570 I pro wifi
Crucial Ballistix Max RGB 4000mhz
cpu Cooler Mugen5 tuf rgb
Case ITX InWin A1

I read somewhere else that i could try using Vcore offset +100 mV, or in another discussion, where the problem was related to the memory, switch VDDCR SOC Voltage to offset mode but don't know if this is the case, and plus i don't know where i can find it in the Gigabyte BIOS ...(not very familiar with it, as i'm a first time gigabyte user). Someone told me to simply don't care about prime95, or to change the infinity fabric to 1600 and the memory frequency to 1800, but in this case while the amd master stress test works, prime95

Can someone please help me ? Really really upset i can't use my new build safely
Do you have the latest bios update for your motherboard? Motherboards often include memory compatibility updates in their Bios releases.
 
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