according to this Microcode Update Document: https://newsroom.intel.com/wp-content/uploads/sites/11/2018/04/microcode-update-guidance.pdf https://newsroom.intel.com/wp-content/uploads/sites/11/2018/04/microcode-update-guidance.pdf, an updated microcode should be available for Arrandale Core i7-620LM (CPUID 20655 => 06-25-05) as its status is now PRODUCTION at revision 0x6.
In the latest version of Linux* Processor Microcode Data File (20180312) https://downloadcenter.intel.com/download/27591/Linux-Processor-Microcode-Data-File?product=873 https://downloadcenter.intel.com/download/27591/Linux-Processor-Microcode-Data-File?product=873 available for download, that update doesn't seem included. How is it possible to obtain it?
Relevant /proc/cpuinfo data:
vendor_id : GenuineIntel
cpu family : 6
model : 37
model name : Intel(R) Core(TM) i7 CPU L 620 @ 2.00GHz
stepping : 5
microcode : 4
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The microcode up updates are applied with a firmware/BIOS update, this following link can provide with more information about the matter
Under the part of useful resources about the issue you can find a list of Operating system and system manufacturers; this may help you to find correct update your system.