Fail to boot due to intel-microcode update

[xf4545]

Issue described in bug: https://bugs.launchpad.net/ubuntu/+source/intel-microcode/+bug/1903883
is still not fixed.
As a temporary fix I can add 'dis_ucode_ldr' parameter to kernel.
Hardware is Acer Aspire v3-372-57M8, i5-6267U, 8GB ram in two modules

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: intel-microcode 3.20201110.0ubuntu0.20.04.2
ProcVersionSignature: Ubuntu 5.4.0-58.64-generic 5.4.73
Uname: Linux 5.4.0-58-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.14
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: XFCE
Date: Sun Dec 20 20:29:25 2020
EcryptfsInUse: Yes
InstallationDate: Installed on 2020-12-11 (8 days ago)
InstallationMedia: Xubuntu 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731)
SourcePackage: intel-microcode
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Andrei (beamflash)]

I see the problem on a Dell Inspiron. /proc/cpuinfo shows

vendor_id : GenuineIntel
cpu family : 6
model : 78
model name : Intel(R) Core(TM) i3-6100U CPU @ 2.30GHz
stepping : 3
microcode : 0xcc

A working version is

intel-microcode/now 3.20190618.0ubuntu0.16.04.1 amd64 [installed,upgradable to: 3.20201110.0ubuntu0.16.04.2]

Upgrading to 3.20201110.0ubuntu0.16.04.2 leads to a freeze on boot: after selecting
an entry in the grub menu there is a message about loading initramfs and the machine becomes
totally unresponsive, needs a hard poweroff. Rolling back to the previous version of intel-microcode restores system to a working state.

[Henrique de Moraes Holschuh (hmh)]

For model 78 stepping 3 processors, look here:

https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/issues/31

To put it bluntly: update your system firmware. If no such update is available, pressure the system vendor into releasing one. For now, that's the only available fix. The alternative is to not attempt to update the processor microcode at all -- and remain vulnerable to the security and reliability issues the microcode update would have fixed.