I also noticed a huge drop in speed of lots of things lately. I ran some Windows updates recently, ref Win 7 Pro 64bit, SW 2018 SP2. BOM sorting and exporting, Copy with Mates, Resolving, and more have been taking longer than expected.. since the update.
I have no omnipotence on this, but I surmise that: because Meltdown exploits have been publicized on Github last week, the cat's out of the bag, and so MS released what patches it could apply from the OS end. I think Intel also is or has been releasing updates for (some of) its processors. Running a free diagnostic utility called InSpectre by GRC displays that I am partially protected from Meltdown/Spectre, and also that my performance is SLOWER.
As much as I dislike jumping to a partially informed conclusion, let alone repeatedly towards the same scapegoat, I think that at some point with existing hardware, we can either be secure or productive. This bothers me. Exceptions do apply, with options such as network segregation or airgapping, in which one can achieve both.
I'd like to understand this better.