Why is CrystalDiskMark showing slower scores with my new build ?

So I upgraded my rig so now it's got a 9600K + z390 Asus Strix-E. My old system was 2500K + Asus P8P67. Also I'm using the same Samsung SSD EVO 850 1TB. I uploaded screen pics and you can easily see the one on the left is somewhat faster. I'm sure in day to day usage I wouldn't noticed but still shouldn't it be maybe slightly faster or at the very least the same ? I used the same Sata cable and the drive is also set at AHCI.

Now if you guys think the speed is still within a normal range, then so be it but I got to know.

Hmm thats odd. On the new build looks like you're testing on a fresh install of Windows 10? Was it installing windows updates in the background? Indexing drives maybe? Maybe try running the test again.

As you had the default background on very likely windows was doing random stuff with the disk after clean install

Did you format the SSD when you installed?

A few possibilities, did you have antivirus installed in the old 7? 10 comes with defender (formerly the security essentials engine). Another is driver differential for the controller. Yet another is a meltdown/spectre patch. Then like others are saying it takes like two days for a new 10 installation to calm TF down..

I wouldn't say 2 days more like 10-15 minuets to install auto install store updates and windows updates

just make sure the disk is idle in task manager (but if you have gone from Windows 7-10 and/or newer motherboard spector and meltdown fixs do affect storage speeds)

It's likely that Windows 7 was using the Samsung NVMe driver whereas your Windows 10 installation was using the Microsoft NVMe driver.

Check the device manager under Storage controllers to see what NVMe driver your Windows 10 installation is using, and try the Samsung one if it lists the generic Microsoft one.