Ryzen 7950X + Windows 11 + P-1 stage2 = lag

[James Heinrich]

I'm very much enjoying my new Ryzen 7950X system, however I'm disappointed by the lag I get when running Prime95 P-1 stage-2. Everything runs just nicely when Prime95 is doing stage-1 or PRP or something not RAM-intensive, but when it switches to stage-2 the lag becomes really annoying. Seen especially when doing things like double-click-open-file, or Win+E to open File Explorer or such things that should be near-instant (and are in stage-1) take anywhere from 1-5 seconds when Prime95 is using RAM. And not all my RAM either, I allocate it 40 of 64GB during the daytime (50 at night).

Relevant hardware/software:
CPU: AMD Ryzen 9 7950X
GPU: GeForce RTX 4090
Mobo: Asus X670E-E Strix
RAM: G.Skill Trident Z5 Neo RGB DDR5-6000 64GB (2x32GB) AMD EXPO
SSD: WD Black SN850X 4TB
Windows 11 Pro
Prime95 v30.8b17

RAM usage is generally around 50-55GB (40 for Prime95 + 10-15 for whatever else I'm doing). 16GB swap file configured on the SSD. I've played with Core Isolation Memory Integrity with no noticeable difference.

Has anyone else noticed something like this? Any suggestions?

[Mark Rose]

If you disable swap, does the lag persist?

[James Heinrich]

Originally Posted by Mark Rose

If you disable swap, does the lag persist?

It persists.

[Jurzal]

Can try to test with lower RAM Frequency.
6000 MT usually is hard already with 32 GB of Ram for Zen 4 memory controller.

Can try 5600 MT, same timings, see if that helps to reduce the lag. If it does, then at least you know where to look into and find a better RAM tune.

If it does not help, then you may want to look into how to reduce the used RAM bandwidth used by p95, not just size. 16 Core Zen 4 can push so many instructions that RAM bandwidth gets fully saturated before capacity is.

[Xyzzy]

What happens if you use fewer cores?

We use only two cores on our 5800X3D.

(We are also running P-1 with version 30.8 build 17, on W11 Home.)

[James Heinrich]

Originally Posted by Xyzzy

What happens if you use fewer cores?
We use only two cores on our 5800X3D.

Since 7950X is two chiplets I run one 8-thread worker on threads 0..15, second on 16..31
I have experimented with running Prime95 on 7 threads/worker, leaving the first core of each chiplet free. It may have made some small difference, I'm not sure, nothing significant though.

I do notice looking at the Task Manager graph that something weird happens to the worker in stage 2. Just by looking at the graph I can tell which one is in stage 2 -- it has these weird dropouts in the kernel times portion, regularly for about 3 seconds every 15 seconds. The worker in stage1 has a solid usage graph.

[Jurzal]

Originally Posted by James Heinrich

Since 7950X is two chiplets I run one 8-thread worker on threads 0..15, second on 16..31
I have experimented with running Prime95 on 7 threads/worker, leaving the first core of each chiplet free. It may have made some small difference, I'm not sure, nothing significant though.

I do notice looking at the Task Manager graph that something weird happens to the worker in stage 2. Just by looking at the graph I can tell which one is in stage 2 -- it has these weird dropouts in the kernel times portion, regularly for about 3 seconds every 15 seconds. The worker in stage1 has a solid usage graph.

For telemetry and sensor reads I suggest using hwinfo64, it is the gold standard software for it. Can see real time telemetry or make logs.

Behavior indeed seems weird, are you running latest BIOS, Chipset Driver from AMD and Windows Update? What are the temperatures?

[James Heinrich]

Not sure what you wanted to see from HWiNFO, I took a general screenshot.

I have the CPU targeting 70°C in the BIOS (rather than the default 90°C) for noise reasons, and it sticks to that target pretty well (can still draw more than its nominal 170W TDP even with only 14/16 cores running).

Windows Update is up-to-date.

There is a newer AMD Chipset Driver v5.01.03.005 that I'll try out.
edit: No change.
Also unplugged an unused ancient 6TB HDD I saw was giving SMART warnings, also no change.

BIOS is v0805 from a few months ago when I got the system, there are a couple newer versions I could try (not sure if I want to try the beta one):

Version 0922 - 2023/02/24
1. Update AGESA version to ComboAM5PI 1.0.0.5 patch C
2. Improve better performance for AMD new CPUs

Version 0925 - 2023/03/15
1.Improve system stability

Version 1003 Beta Version - 2023/03/20
1. Update AGESA version to ComboAM5PI 1.0.0.6
2. Supports high density DDR5 module
3. TPM 2.0 security update

[Xyzzy]

So what happens if you run just 1 core per chiplet?



Also, we run without HT enabled. What happens if you try that?

[James Heinrich]

Originally Posted by Xyzzy

So what happens if you run just 1 core per chiplet?

P-1 runs 8x slower than it could?


I updated BIOS to v1003-beta but no change in lagginess (and same weird dips on the CPU graph).

But I did lose my 70°C thermal limit BIOS option so my fans are screaming at me. :down:
I'll have to check again for that option, maybe they renamed/moved it.
edit: found it -- you need to set Precision Boost Overdrive mode to "Enhancement" (not Auto or Manual or any of the other half-dozen options) to be able to see it).

[Xyzzy]

Originally Posted by James Heinrich

P-1 runs 8x slower than it could?

It probably won't run exactly 8× slower.

CORESPERCHIPLET = 1
TEST P-1
    IF LAG == TRUE
        CORESPERCHIPLET--
    ELSE
        CORESPERCHIPLET++