Own memory scan - why so slooow?

Comodo Internet Security - CIS AntiVirus Help - CIS
#1

Own memory scan - why so slooow?

I use CFW with antivirus. The default av scans (quick, full, or folder scan) are very fast.
I created an own “ram-only” scan. Option: all the default, except: don’t scan zip files.
And this scan is very very slooow! But why?
My PC: core i5 8 GB RAM win8x64.

Thanks