from last message, I kept find the problem and research, I saw most user have same problem, the microcode effect the performance, so I hope can fix this problem, and downgrade the bios version is can't change the microcode!
You can rollback to the previous BIOS version (no interest if the previous one was 1.2.3) by doing so :
Unplugg AC power,
HIT CTRL-ESC for few seconds
plug AC and power on
HIT F2 -> a specific BIOS menu will appear on which you will see "Rollback to previous Version" Menu
NB / there is only one previous version