I am using an Asrock Fatal1ty B450 Gaming K4 and basically everything is fine, except a small issue. I have Corsair Vengeance LPX DIMM Kit 8GB, DDR4-3000, CL15-17-17-35 (CMK8GX4M2B3000C15), the XMP Profile is shown correcty, but set wrong.

Read out: 15-17-17-35 

Set to: 16-17-17-35 

Could it be a Bios Bug? 

Following additional hardware is used:

Raven Ridge APU 2200G 
Intel SSD 600p 256GB 
be quiet! Pure Power 10-CM 400W 

Thanks in advance!

its because you have geardown mode enabled

this when switched on stops all ram from using the odd numbered timing on primary number

eg cl15 shows as cl15 until windows boots then is forced to be cl16

cl13 would be forced to be cl14 etc etc

its an amd bios thing

Tried to disable Gear Down Mode, but then the system just boot in fail save mode (DDR4 2133), so I leave it enabled and work with CL16 (very stable and no issues).

EDIT:

Just tried to set manually to CL14, system booted, checked setting with CPU-Z and system was set to CL14...

Then tried to set it to CL15 and it ended in CL16 again... strange...

no its not its exactly as i said

geardown enabled wont allow cl15 or cl17 or cl13 etc

it will allow even numbers like 12/14/16/18

if you can tweak things to get cl14 stable then great it'll help a little in all pc tasks and games

just disabling geardown dosnt usually work anyway you tend to have to set up bank group swap etc to suit your ram and maybe bump the volts etc

there is a lot of logic to just leaving it stable at xmp ,rather than chase tighter or faster timings that may take ages to find stable

I tell you, 15 years ago, overclocking / tweaking was much easier

haha yes

we either booted the athlonx2 at a faster speed or it didnt ...............

we didnt have as many bios options either by quite an amount less.........

Thanks for your help!