Linux / X470 Taichi hangs

This is in the way of a "public service announcement", specifically for the X470 Taichi Ultimate but I suspect that similar problems might exist on other boards.

Build is a 2700X in a Taichi Ultimate, RX 550 graphics. I had been extremely stable on kernel 4.17.19 and later since last summer, until I updated my BIOS to the 2.00 version. I started getting occasional freezes, where the entire machine would lock up hard with nothing in the MCE logs or anywhere else. I was blaming this on the RX 550 (and indeed the amdgpu driver has its issues), but with kernel 5.0.x it got so that a freeze would happen within minutes.

The cure turns out to be to avoid deep C-states. The older BIOS had a "disable C6 state" option, which is apparently gone in the new version. I haven't yet figured out whether a kernel command line of "processor.max_cstates=1" suffices, or whether one needs to disable Global C-States entirely in the BIOS (OC Tweaker, AMD CBS, CPU options); the difference is some 10 watts at idle which is minimal. I can say that "processor.max_cstates=5" does NOT work to avoid the hangs.

It's only been a day so far, but that's more uptime than I've had in a couple weeks. Other input welcome.

Not here, kernel 5.0.5.
I?™m also testing deeply the ram @3466 (rated @3200) with no issues so far.

paologab wrote: Not here, kernel 5.0.5. I?�m also testing deeply the ram @3466 (rated @3200) with no issues so far.

5.0.5 hung just as often as any other 5.0.x for me.