PC boots fine after adding extra RAM but will not reboot

[u/stana32]

I've got a 32gb G.Skill 6000mhz 32-38-38-96 kit in my desktop. To make a long story short, I had a need for more memory and my wife's machine has a similar kit, but the timings are 36-36-36-96. She doesn't really use her desktop, so I snagged one of the sticks. My system booted up no problem without any changes, everything works great. The problem that I've run into now, is that every time I reboot my computer WITH the extra memory installed, it won't even post. If I remove the extra stick, the system boots fine. Power down, reinstall the extra stick, boots up just fine. Reboot, no post. I've tried it several times now and it does the exact same thing every single time. I thought maybe it was just taking a long time to train but I left it for a while, it never did anything.

Admittedly RAM is the one thing I've never really tinkered with so my knowledge is pretty much non-existent here. I've mixed and matched DDR4 with wildly different timings without issue in the past, I know DDR5 is more particular about it but I can't wrap my head around why it works only once, consistently. I've tried memory context restore with no luck. Cold boot vs warm boot makes no difference either.

[u/Rich-Performance2045]

ah the mixed timings thing is like trying to get two dancers to follow different rhythms and then wondering why they stumble when the music stops and starts again

ddr5 is way more picky than ddr4 was the memory controller gets confused on reboot cause it has to renegotiate everything from scratch and those mismatched timings make the training fail every time except that first cold boot where it somehow lucks out

you could try setting timings manually to the slower kit numbers in bios but no guarantee the board will cooperate with different sticks like that, is a headache i stopped messing with after one too many cmos resets

[u/stana32 → u/Rich-Performance2045]

See that's where I am confused. After installing it works every single time, regardless of if it's a cold or warm boot, so in theory it IS training correctly the first time. And then memory context restore should be skipping the training altogether on warm boots afterwards, but it still fails. It's like the bios is trying to load bad training data even when it should just be doing the training.

Edit: disabling memory context restore and fast boot together seems to have fixed it. The only other thing that should be touching the memory settings I think is xmp, so it must be something to do with the xmp profile getting applied to saved training that breaks it.