Hey guys,
 
I wanted to do some stability test on my system so i've tried to disable all the power saving features on my PC to get the most reliable results.
 
But whatever the settings i apply, i can't manage to get a fixed CPU frequency because the FSB/BCLK frequency is constantly slightly fluctuating between 99.68 MHz and 99.81 MHz (checked with evga eleet utility). My windows 10 is set to "max performance" in the power setting so the turbo values do not change and CPU frequency only fluctuates slightly because of the FSB between 4585.42 MHz and 4591.03 MHz
 
I searched a bit on the net about this before posting and some informations suggest this could be linked to the spread spectrum mechanism, but there is no option to disable it in the z370 ftw bios afaik. I understand spread spectrum helps preventing getting electromagnetic interferences and to comply with EMI regulations, but i'm not using my computer close to any EM sensitive device in my house and the variable FSB/BCLK can't be a good thing for stability.
 
Here are my current bios settings (using latest 1.18 bios):
 
https://1drv.ms/f/s!AuxWrtCtPteFmz-jNkDdKZ52yXrz?e=cqZ0VA
 
Note that this small FSB fluctuation doesn't prevent my system to be stable but i'd prefer to be able to get rid of it if possible.
 
Things i've tried with no results so far:
 
- changing BCLK (FSB) slightly in the bios,
- changing CPU settings in the bios (can't disable EIST or turbo mode is also disabled and CPU wont go over 3600 Mhz),
- checking with other monitoring softwares (they all report the same thing),
 
Any ideas? Thanks!

Well i wasn't able to disable spread spectrum fully, but found this: https://xdevs.com/guide/e399ocg/#sscg
 
"Because BCLK receiver use only clock edges to provide accurate timing, spread spectrum is not affecting normal CPU functions, thus allowing noticeable improvement of the EMC. Intel specifications allow use of 0.2% down-spread, which means BCLK is modulated to 99.8 – 100.00 MHz frequency range, instead of single 100.00 MHz clock peak. Due to this momentary frequency measurements of the BCLK will return random value between 99.8 and 100.00 MHz, reflected in same CPU and memory clock variation."
 
So if i understand correctly this means even if monitoring softwares report a variating BCLK and cpu frequency due to spread spectrum, the effective cpu frequency does not change and uses a stable bclk value of 100.
 
So apparently disableing this is not needed, but then some other recent motherboards seem to still offer an option to disable this. So is it really just a display issue? I'm not 100% conviced but can't do much about it anyway.