Hi guys, I am hoping someone can shed some light on this. I am not sure if this is expected behavior. When I overclock my 9800X and run an AVX load (handbrake or prime95) my clock speed constantly fluctuates between my actual overclock and the AVX offset. Basically it will not stay at the offset clock. For example I have my CPU overclocked to 4.6 with AVX offset of 5. But when I run handbrake my clock jumps between 4.1 and 4.6 every second or two. Then it sometimes will blue screen, I am guessing because it wont just stay at 4.1 like its supposed to. I notice this behavior by looking at the graph in MSI Afterburner. It happens so fast CPUZ doesnt always pick it up. How can I get my AVX offset to stay put under load?

BIOS version is 1.17. Although I have tried others and they all give the same result. My memory is G Skill running at XMP 3733Mhz. PSU is EVGA 1600T2. I'm not at home so I cant see logs right now but I'm pretty sure it's the clock speed fluctuation that causes the crash. Its rock solid stable under non-AVX load and the clock stays steady at 4.6Ghz. It's only when using AVX offset that the speed fluctuates. It's ever so slight and can only be seen in Afterburner using the graphs. It will be running at the offset speed of 4.1 and just jump up to 4.6 for like half a second, but it does this constantly every second or two. I can show a screenshot when I get home. I have no problems with non-AVX and no problems if not overclocked, both scenarios have the clock stay stable. It's just OCed AVX. It just seems like it doesn't want to honor the offset, it just keeps wanting to jump back to 4.6.

bcavnaugh
What are to Two Off Sets you are running now?
AVX2=
AVX3=
CPU Core OC Setting?
Is the Memory XMP Profile changing your BCLK Setting?

AVX2 is set to 5. AVX3 is also set to 5. All CPU cores are all set to 46. Not sure about the BCLK setting, I'll have to check and post back.

bcavnaugh

willdearborn

bcavnaugh
What are to Two Off Sets you are running now?
AVX2=
AVX3=
CPU Core OC Setting?
Is the Memory XMP Profile changing your BCLK Setting?

AVX2 is set to 5. AVX3 is also set to 5. All CPU cores are all set to 46. Not sure about the BCLK setting, I'll have to check and post back.

Some Not all Memory XMP Profiles change it so why I ask.
AVX2=2
AVX3=3
46 on mine and 44 on another. Benchmarking @ 5
What are you using to Cool the CPU?
 

I'll have to check on BLCK. But I really dont think this has to do with memory. Eveything is fine and stable. Temps are fine. Eveything is fine, except that the clock speed jumps up from offset to non-offset when under AVX load, like handbrake. It feels like it's a BIOS setting of some sort, but I've looked everywhere and nothing I can see really makes sense that it would effect this. I was hoping I missed something in the BIOS.

bcavnaugh
My understanding is if your clock is set at 4600MHz and you have an AVX offset of 5 your clock will drop to 4100MHz when an application that uses AVX.
That is the Job of having this setting(s) in the Bios.
Our X299 have an AVX2 and AVX3 and the Z3xx have only a single AVX setting in the Bios.

Yes I agree, that it how I understand it is supposed to work as well. But for some reason mine jumps up and down between OCed clock and offset clock when running AVX. Here is a screenshot of the clock speed graph in afterburner. You can see it's steady at 4.6 and then as soon as I run handbrake that is when it goes down to 4.1 (as it should) but then a few seconds later it's back to 4.6 and just goes up and down from there:

 

bcavnaugh
What AXV are you running?
Is the C States Disabled in the Bios?

I am not sure exactly. It's whatever handbrake and prime95 use. It happens in both applications. I cannot seem to find if handbrake uses AVX 512 or not.
 
C-states are enabled. Could that be it? I'll try and disable now.
 
And to answer a previous question, XMP left my BCLK unaltered at 100.00

No luck with the C states setting. I tried disabling it and the clock fluctuation still happens. If anyone has any ideas let me know. One good thing is that during the testing I have been doing today it hasn't blue screened or crashed at all. I'd still like to know why it's happening though. It can't be good for stability.

Power plan is set to high performance

I'd be interested to know if it happens on your system too when running handbrake. And wow that's interesting that you limit your system to 8 cores when running it. Using as many threads as possible to do encoding was a big reason I went with X299. I guess I'll have to do some testing to see about negative returns with more threads. I have no UPS so power draw isn't a concern for me.

GGTV-Jon
I should have said diminishing returns on added cores versus heat and power draw, not really a negative performance drop.

Oh ok..gotcha.

Also if anyone has noticed this clock speed fluctuation or knows how to correct it, please post.

cdc-951
Correct me if I am wrong, but AVX is heavy loads, so you might be power limited (Maybe a bios setting can lift power limit) or you are thermal throttling. AVX is a heavy load on intel cpus and so avx offset is to force an underclock when AVX loads kick on. Prevents high ghz users from burning their cpu as avx hits the cache, memory controller and the whole die a lot more spread out and faster than non avx work loads. Think of it as almost all the transistors are almost at full blast.

 
Maybe I didn't explain it properly. I understand what the AVX offset is. My temps are fine. No core goes above 75 under full AVX load. I am not power limited or throttling in anyway. The problem is the exact opposite. It will NOT STAY downclocked under AVX load. It starts out at the AVX offset clock of 4.1GHz and the jumps back up to 4.6 and then back and forth between 4.1 and 4.6 continuously while under load. As evidenced by my screenshot:

As you can see the clock speed starts out as the flat line 4.6Ghz while the CPU is idle. Then when I run handbrake or prime95 (AVX loads) that is when the clock speed goes down to 4.1 which is correct. The problem lies in when it jumps back up and down after that. It can be seen in the graph.
 
Now the good news is that after a tiny pit of voltage tweaking my system seems to be stable under both AVX and non-AVX loads. I ran handbrake for 24 hours with no crashes. Maybe I am making something out of nothing with the clock speed jumping up and down like that since it doesn't seem to affect stability.

Adding to my other post... I am wondering if there is like a very small amount of time that Prime95 is not actually loading the CPU with AVX instructions so the CPU frequency fluctuates like you are seeing. I have not noticed this with my setup, but I am not using the MSI software to monitor the CPU I am using the HWInfo65 software mentioned above. I will run the Prime95 software on my system tonight and monitor with the MSI software and report back. 

So did some testing with my 9800x and MSI Afterburner... I do not have the fluctuating CPU frequency it holds steady at the correct frequency. Would be really curious to see that HWInfo64 log file to see what exactly is happening when it changes the CPU frequency like that. 
 
Did some  more testing and was able to get MSI Afterburner to show the fluctuating CPU frequency.  

bcavnaugh
I do not use or trust HWInfo64 myself.
I use AIDA64 Extreme.
But no software will ever show the same value for the same sensor.

I wish EVGA would come out with something similar maybe tie into Precision or something. Out of curiosity why dont you trust HWInfo64?     

Sorry I have not been able to do some testing and report back - was having radiator fan issues = subpar cooling performance. New fans are now in the system, should be able to do some testing this weekend