First: I only have experience on Linux, with an i3 and 12 GB memory.
dbcache size was already set to 2048MB, which was not seemed to work.
I have never increased dbcache, it's set to the default 300 MB.
type D:\Bitcoin\data\chainstate\*.* > nul
3.Wait for the command to complete (took me about 5min).
I just tested "cat * > /dev/null", it took 0.685 seconds. That means the whole thing is in filecache already.
If reading 3 GB takes 5 minutes, you only get 10 MB/s. My guess is your hdd is fragmented too much.
Dramatic things then happened: bitcoin-qt was significantly "boosted up". Time consumed by validating each block has shrunk to only several seconds!
This is the speed I am used to.
I wonder if I made any mistakes? Doing such "manual optimization" is so strange...
I've seen many more threads about performance problems on Windows. I haven't used Windows in a long time, but my guess would be it's just bad at memory management.
I put my chainstate directory on my SSD a couple of months back, and created a simlink to that location. Note: this is not recommended for security reasons (but I don't worry about these).
This improved my Bitcoin Core startup time from 80 to 20 seconds. I would expect your slow fragmented chainstate to be much faster from SSD.