Issue with F4-3600C16D-64GTZR on an MSI Tomahawk B550 motherboard

[lococola]

Since 2021 I have been running the MSI Tomahawk B550 with a set of G.Skill F4-3600C16D-32GTZR memory, a total of 32 GB at 16-16-16-36 timings (no overclock). This is using the built in XMP-1 profile. I have had not a single issue. Using slots 2 and 4 on the motherboard.

Today I swapped the ram for basically the same, but 64 GB this time, the F4-3600C16D-64GTZR ram kit. Same slots 2 and 4 on the mobo. But now it won't boot to BIOS. The screen stays black and the first EZ led is burning red, which apparently means a CPU issue.

However, when I swap the ram back to the 32 GB kit, I can boot again and there are no issues.
What can I do to fix this? It stands to reason if the F4-3600C16D-32GTZR is supported, so should the F4-3600C16D-64GTZR.

[lococola]

And..... fixed! Didn't have to clear the CMOS, just optimizing to defaults was enough for the RAM to get recognized properly. I think the issue was I still had XMP enabled, and that's why the BIOS had problems with the new ram, as the timings are different. Silly of me not to think of that beforehand. But all good now, F4-3600C16D-64GTZR with XMP profile 1 at 3600 Mhz 16-22-22-42.

[emissary42]

It is a fairly common issue. The motherboard should initialize a safe boot after a couple of failed attempts to start with the old settings, but sometimes that just won't happen. Then you have to clear the CMOS manually. With some motherboards it is also possible to force a safe boot by flipping the switch on the power supply during POST.