When does Ryzen CPU retrain memory

[Islam Ghunym]

I am looking for an absolute answer for the title.

 

I am configuring an old Ryzen picasso chip 3400G on the latest AGEISA firmware. I wonder if the CPU retrain the memory every time I change any of the memory timings. To what I know is that it retrains the memory at each timing change, but I started doubting that recently. Perhaps it doesn't do that always (depends on the specific timings that were cganged) and it is also possible theoretically to change timings without retraining (like Intel realtime memory tuning)

[RONOTHAN##]

2 hours ago, Islam Ghunym said:

wonder if the CPU retrain the memory every time I change any of the memory timings.

Yes.

 

AM4 in my experience does a retrain on every reboot, regardless of whether you change anything or not. There are supposedly ways to get it to skip training (I've never figured them out, and it doesn't take long enough to really care anyway), but it does require a retrain for any adjustment made to the memory system (timing, termination, voltage, etc.) so if you're tuning memory, you'll be retraining every time you enter the BIOS. 

 

2 hours ago, Islam Ghunym said:

it is also possible theoretically to change timings without retraining (like Intel realtime memory tuning)

From what I remember, a feature similar to that was supposed to be released alongside Ryzen 9000 (I think it was an upgraded version of EXPO but could be wrong), though I don't believe it actually did (and if it did, it's been so massively overshadowed by the other issues of that launch that it's impossible to find evidence of it being used). It won't work on AM4 though, there needs to be explicit BIOS and CPU support that just doesn't exist on the AM4 chips.