Upgraded from 16gb to 32gb of DDR4 Ram, won't boot bast 2666mhz

[zzenn]

So I just upgraded the ram in my computer from 16gb of DDR4 3000mhz ram to 32gb. Same ram, identical sticks etc. My 16gb ran fine at the 3000mhz profile. but when I added the two new ones, it failed to boot, and stocked at 2133mhz. I eventually changed the frequency one by one to eventually get to 2666 and it failed at 2733. So my question is why is this happening? My mother board is rated for 64gb 3000mhz. I have the Asus ROG Strix B450-F motherboard with a Ryzen 2700x. The ram is 8gb sticks each of TridentZ G-skill.

So why would it not boot using the XMP profile it has set? Is there something else that I need to do to fix this? Any responses would be great! Thanks!

 

[kanewolf]

Not unexpected. Four DIMMs puts more load on the memory controller circuits. They just can't run as high clock speed. A CPU with dual channel memory is optimized to use two DIMMs. You might be able to add a little RAM voltage or you may never get it to work.

And just because they are "identical" part numbers and specs doesn't mean they are identical. Vendors sell matched sets for a reason. You have two matched sets of two DIMMs. You don't have a matched set of four DIMMs.

 

[Calvin7]

Memory manufacturers won't guarantee such a combination to be compatible together.

XMP settings are for the memory in the form it was sold and not for other combinations you decide to make.

Memory is guaranteed in the form sold. Use of identical, same thing, exact match may raise the odds of the memory being compatible together instead of using random modules but have no guarantee to be compatible together.

Workarounds to get extra memory to work include:
Lower memory clock speed
Relax DRAM timings
Increase DRAM voltage