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Build Identifier: 

If the current Tumbleweed version of ucode-amd is installed (20191118-1.1) then
the machine resets just after GRUB as the kernel is being loaded. If ucode-amd
is downgraded to the version in Leap 15.1 (20190618-lp151.2.6.1) the machine
boots successfully.

Reproducible: Always

Steps to Reproduce:
1. Create a live USB image of Tumbleweed (tested 20191228)
2. Boot from this USB stick
3. Hit ENTER on the default selection in GRUB, or wait for it to time-out
Actual Results:  
Grub prints "Loading initial ramdisk", then the machine immediately resets.

Expected Results:  
Grub prints "Loading initial ramdisk", then the boot sequence proceeds.

The machine has dual AMD EPYC 7282 16-core processors and a Supermicro
H11DSi-NT motherboard.

The failure seems to occur before the kernel is loaded, so loglevel parameters
do not result in any useful data being printed before the reset. 

The problem can be reproduced either with a live USB stick or with a fresh
install of Tumbleweed with default settings. Deselecting "ucode-amd" in the
installer resolves the issue. Installing "ucode-amd" from the Leap 15.1 update
repository also results in a functional system. It is just the version of
"ucode-amd" in Tumbleweed (and Leap 15.2) that appears to be the issue.