Comment # 13 on bug 987358 from Takashi Iwai

(In reply to Cristian Rodr�guez from comment #12)
> Hi Michal.. do you know how to debug a hang during the initrd loading or the
> early microcode stuff ?

Try to pass dis_ucode_ldr boot option.  This will disable the early microcode
loading.

If this helps, it implies that the ucode is the culprit.  You can try to
downgrade the ucode-intel package.