[CentOS] Boot process slow with rhgb quiet on

If I boot with "rhgb quiet" off, my computer boots in 1 minute and 30 
seconds.

If I boot with "rhgb quiet" on, my computer boots in 3m11s. That's a 
long time to wait.

Significantly, when booting with "rhgb quiet", right at the moment X 
takes over, there is a 1m36s pause where the screen is blank except for 
the hourglass cursor turning around and around.

Of course, if my main priority was to simply boot quickly, I would 
simply remove the "rhgb quiet" option from the boot process. And I'm not 
opposed to doing that.

However, this pause only started happening recently, so I wonder why it 
exists at all.

When booting with "rhgb quiet" off, I tried to look for any errors or 
indications of a problem, but it seemed to boot mostly without pause or 
error. There was one message which was like an error warning, which said 
something about a "microcode device doesn't exist?". But text was moving 
across the screen quickly and I couldn't write down exactly what it said.

Before I give in and remove the "rhgb quiet" option permanently, is 
there any way I might be able to diagnose and fix this delay problem? 
I'd rather be telling the computer how to boot, instead of it telling me.

Dave